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Full text of "NFPA NEC (2002): National Electrical Code"

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NFPA NEC (2002), the National Electrical Code, 
as incorporated and mandated by the States and 
Municipalities of Winfield (Kansas), Indiana, 
Minnesota, New York City (New York), et. alia., 
and in the Code of Federal Regulations at 
10 CFR 431.326 et. seq. 



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NATIONAL ELECTRICAL CO 



INTERNATIONAL ELECTRICAL CODE SERIES 



CODE 



NFPA AN INTERNATIONAL CODES AND STANDARDS ORGANIZATION 




NFPA AN INTERNATIONAL CODES AND STANDARDS ORGANIZATION 



70-1 



Copyright © 2001, National Fire Protection Association, All Rights Reserved 

NFPA 70 
National Electrical Code® 

2002 Edition 

This edition of NFPA 70, National Electrical Code, was prepared by the National Elec- 
trical Code Committee and acted on by the National Fire Protection Association, Inc., at its 
May Association Technical Meeting held May 13-17, 2001, in Anaheim, CA. It was issued 
by the Standards Council on July 13, 2001, with an effective date of August 2, 2001, and 
supersedes all previous editions. 

This edition of NFPA 70 was approved as an American National Standard on August 2, 
2001. 

History and Development of the National Electrical Code 

The National Fire Protection Association has acted as sponsor of the National Electrical 
Code since 1911. The original Code document was developed in 1897 as a result of the 
united efforts of various insurance, electrical, architectural, and allied interests. 

In accordance with the provisions of the NFPA Regulations Governing Committee 
Projects, a National Electrical Code Committee Report on Proposals containing proposed 
amendments to the 1999 National Electrical Code was published by the NFPA in July 2000. 
This report recorded the actions of the various Code-Making Panels and the Correlating 
Committee of the National Electrical Code Committee on each proposal that had been made 
to revise the 1999 Code. The report was circulated to all members of the National Electrical 
Code Committee and was made available to other interested NFPA members and to the 
public for review and comment. Following the close of the public comment period, the 
Code-Making Panels met, acted on each comment, and reported their action to the Corre- 
lating Committee. The NFPA published the National Electrical Code Committee Report on 
Comments in April 2001, which recorded the actions of the Code-Making Panels and the 
Correlating Committee on each public comment to the National Electrical Code Committee 
Report on Proposals. The National Electrical Code Committee Report on Proposals and the 
National Electrical Code Committee Report on Comments were presented to the 2001 May 
Association Technical Meeting for adoption. 

NFPA has an Electrical Section that provides particular opportunity for NFPA members 
interested in electrical safety to become better informed and to contribute to the develop- 
ment of the National Electrical Code and other NFPA electrical standards. Each of the 
Code-Making Panels and the Chairman of the Correlating Committee reported their recom- 
mendations to meetings of the Electrical Section at the 2001 NFPA World Fire Safety 
Congress and Exposition. The Electrical Section thus had opportunity to discuss and review 
the report of the National Electrical Code Committee prior to the adoption of this edition of 
the Code by the Association at its 2001 May Technical Session. 

This 2002 edition supersedes all other previous editions, supplements, and printings 
dated 1897, 1899, 1901, 1903, 1904, 1905, 1907, 1909, 1911, 1913, 1915, 1918, 1920, 1923, 
1925, 1926, 1928, 1930, 1931, 1933, 1935, 1937, 1940, 1942, 1943, 1947, 1949, 1951, 
1953, 1954, 1955, 1956, 1957, 1958, 1959, 1962, 1965, 1968, 1971, 1975, 1978, 1981, 
1984, 1987, 1990, 1993, 1996, and 1999. 

New or revised technical content in this edition is indicated by a vertical rule next to the 
paragraph, table, or figure in which the change occurred. 

This Code is purely advisory as far as NFPA is concerned. It is made available for a wide 
variety of both public and private uses in the interest of life and property protection. 
These include both use in law and for regulatory purposes, and use in private self -regulation 
and standardization activities as insurance underwriting, building and facilities construction 
and management, and product testing and certification. 

NATIONAL ELECTRICAL CODE 2002 Edition 



70-2 



CONTENTS 



Contents 



ARTICLE 

80 Administration and Enforcement 70- 23 

90 Introduction 70- 29 

Chapter 1 General 

100 Definitions 70- 33 

I. General 70- 33 

II. Over 600 Volts, Nominal 70- 39 

110 Requirements for Electrical Installations 70- 40 

I. General 70- 40 

II. 600 Volts, Nominal, or Less 70- 43 

III. Over 600 Volts, Nominal 70- 45 

IV. Tunnel Installations over 600 Volts, 

Nominal 70- 47 

Chapter 2 Wiring and Protection 

200 Use and Identification of Grounded 

Conductors 70- 49 

210 Branch Circuits 70-51 

I. General Provisions 70- 5 1 

II. Branch-Circuit Ratings 70- 54 

III. Required Outlets 70- 57 

215 Feeders 70- 60 

220 Branch-Circuit, Feeder, and Service 

Calculations 70- 61 

I. General 70- 61 

II. Feeders and Services 70- 63 

III. Optional Calculations for Computing 

Feeder and Service Loads 70- 66 

IV. Method for Computing Farm Loads 70- 69 

225 Outside Branch Circuits and Feeders 70- 69 

I. General 70- 70 

II. More Than One Building or Other 

Structure 70- 72 

III. Over 600 Volts 70- 74 

230 Services 70- 75 

I. General 70- 75 

II. Overhead Service-Drop Conductors 70- 77 

III. Underground Service-Lateral 

Conductors 70- 78 

IV Service-Entrance Conductors 70- 78 

V Service Equipment — General 70- 8 1 

VI. Service Equipment — Disconnecting 

Means 70- 81 

VII. Service Equipment — Overcurrent 

Protection 70- 82 

VIII. Services Exceeding 600 Volts, Nominal .... 70- 84 

240 Overcurrent Protection 70- 85 

I. General 70- 85 

II. Location 70- 88 



ARTICLE 

III. Enclosures 70- 91 

IV Disconnecting and Guarding 70- 92 

V. Plug Fuses, Fuseholders, and Adapters 70- 92 

VI. Cartridge Fuses and Fuseholders 70- 93 

VII. Circuit Breakers 70- 93 

VIII. Supervised Industrial Installations 70- 94 

IX. Overcurrent Protection Over 600 Volts, 

Nominal 70- 95 

250 Grounding 70- 95 

I. General 70- 95 

II. Circuit and System Grounding 70- 98 

III. Grounding Electrode System and 

Grounding Electrode Conductor 70-104 

IV. Enclosure, Raceway, and Service Cable 
Grounding 70-108 

V Bonding 70-108 

VI. Equipment Grounding and Equipment 

Grounding Conductors 70-1 1 1 

VII. Methods of Equipment Grounding 70-115 

VIII. Direct-Current Systems 70-117 

IX. Instruments, Meters, and Relays 70-1 1 8 

X. Grounding of Systems and Circuits of 

1 kV and Over (High Voltage) 70-119 

280 Surge Arresters 70-120 

I. General 70-120 

II. Installation 70-121 

III. Connecting Surge Arresters 70-121 

285 Transient Voltage Surge Suppressors: 

TVSSs 70-122 

I. General 70-122 

II. Installation 70-122 

III. Connecting Transient Voltage Surge 

Suppressors 70-122 

Chapter 3 Wiring Methods and Materials 

300 Wiring Methods 70-123 

I. General Requirements 70-123 

II. Requirements for Over 600 Volts, 

Nominal 70-132 

310 Conductors for General Wiring 70-133 

312 Cabinets, Cutout Boxes, and Meter Socket 

Enclosures 70-161 

I. Installation 70-161 

II. Construction Specifications 70-162 

314 Outlet, Device, Pull, and Junction Boxes; 

Conduit Bodies; Fittings; and Manholes 70-164 

I. Scope and General 70-164 

II. Installation 70-165 

III. Construction Specifications 70-170 

IV Manholes and Other Electric 

Enclosures Intended for Personnel 

Entry 70-171 



2002 Edition 



NATIONAL ELECTRICAL CODE 



CONTENTS 



70-3 



ARTICLE 

V. Pull and Junction Boxes for Use on 

Systems Over 600 Volts, Nominal 70-172 

320 Armored Cable: Type AC 70-173 

I. General 70-173 

II. Installation 70-173 

III. Construction Specifications 70-174 

322 Flat Cable Assemblies: Type FC 70-174 

I. General 70-174 

II. Installation 70-174 

III. Construction 70-175 

324 Flat Conductor Cable: Type FCC 70-175 

I. General 70-175 

II. Installation 70-176 

III. Construction 70-177 

326 Integrated Gas Spacer Cable: Type IGS 70-178 

I. General 70-178 

II. Installation 70-178 

III. Construction Specifications 70-178 

328 Medium Voltage Cable: Type MV 70-179 

I. General 70-179 

II. Installation 70-179 

III. Construction Specifications 70-179 

330 Metal-Clad Cable: Type MC 70-179 

I. General 70-179 

II. Installation 70-179 

III. Construction Specifications 70-181 

332 Mineral-Insulated, Metal-Sheathed Cable: 

Type MI 70-181 

I. General 70-181 

II. Installation 70-181 

III. Construction Specifications 70-182 

334 Nonmetallic-Sheathed Cable: Types NM, 

NMC, andNMS 70-182 

I. General 70-182 

H. Installation 70-182 

III. Construction Specifications 70-184 

336 Power and Control Tray Cable: Type TC 70-1 84 

I. General 70-184 

II. Installation 70-185 

III. Construction Specifications 70-185 

338 Service-Entrance Cable: Types SE and 

USE 70-186 

I. General 70-186 

II. Installation 70-186 

III. Construction 70-186 

340 Underground Feeder and Branch-Circuit 

Cable: Type UF 70-187 

I. General 70-187 

II. Installation 70-187 

III. Construction Specifications 70-187 



ARTICLE 

342 Intermediate Metal Conduit: Type IMC 70-1 87 

I. General 70-187 

II. Installation 70-188 

III. Construction Specifications 70-189 

344 Rigid Metal Conduit: Type RMC 70-1 89 

I. General 70-189 

II. Installation 70-189 

III. Construction Specifications 70-191 

348 Flexible Metal Conduit: Type FMC 70-191 

I. General 70-191 

II. Installation 70-191 

350 Liquidtight Flexible Metal Conduit: Type 

LFMC 70-192 

I. General 70-192 

II. Installation 70-193 

III. Construction Specifications 70-193 

352 Rigid Nonmetallic Conduit: Type RNC 70-194 

I. General 70-194 

II. Installation 70-194 

III. Construction Specifications 70-195 

354 Nonmetallic Underground Conduit with 

Conductors: Type NUCC 70-197 

I. General 70-197 

II. Installation 70-197 

III. Construction Specifications 70-198 

356 Liquidtight Flexible Nonmetallic Conduit: 

TypeLFNC 70-198 

I. General 70-198 

II. Installation 70-198 

III. Construction Specifications 70-199 

358 Electrical Metallic Tubing: Type EMT 70-200 

I. General 70-200 

II. Installation 70-200 

III. Construction Specifications 70-20 1 

360 Flexible Metallic Tubing: Type FMT 70-20 1 

I. General 70-201 

II. Installation 70-201 

III. Construction Specifications 70-202 

362 Electrical Nonmetallic Tubing: Type ENT .... 70-202 

I. General 70-202 

II. Installation 70-202 

III. Construction Specifications 70-204 

366 Auxiliary Gutters 70-204 

368 Busways 70-206 

I. General Requirements 70-206 

II. Requirements for Over 600 Volts, 

Nominal 70-207 

370 Cablebus 70-208 

372 Cellular Concrete Floor Raceways 70-209 



NATIONAL ELECTRICAL CODE 



2002 Edition 



70-4 



CONTENTS 



ARTICLE 

374 Cellular Metal Floor Raceways 70-2 1 

I. Installation 70-210 

II. Construction Specifications 70-211 

376 Metal Wireways 70-211 

I. General 70-211 

II. Installation 70-211 

III. Construction Specifications 70-212 

378 Nonmetallic Wireways 70-212 

I. General 70-212 

II. Installation 70-212 

III. Construction Specifications 70-2 1 3 

380 Multioutlet Assembly 70-213 

382 Nonmetallic Extensions 70-214 

I. Genera] 70-214 

II. Installation 70-214 

384 Strut-Type Channel Raceway 70-215 

I. General 70-215 

II. Installation 70-215 

III. Construction Specifications 70-216 

386 Surface Metal Raceways 70-216 

I. General 70-216 

II. Installation 70-216 

III. Construction Specifications 70-217 

388 Surface Nonmetallic Raceways 70-217 

I. General 70-217 

II. Installation 70-217 

III. Construction Specifications 70-2 1 8 

390 Underfloor Raceways 70-218 

392 Cable Trays 70-219 

394 Concealed Knob-and-Tube Wiring 70-225 

I. General 70-225 

II. Installation 70-226 

III. Construction Specifications 70-226 

396 Messenger Supported Wiring 70-227 

I. General 70-227 

II. Installation 70-227 

398 Open Wiring on Insulators 70-227 

I. General 70-227 

II. Installation 70-227 

III. Construction Specifications 70-229 

Chapter 4 Equipment for General Use 

400 Flexible Cords and Cables 70-231 

I. General 70-231 

II. Construction Specifications 70-239 

III. Portable Cables Over 600 Volts, 

Nominal 70-240 

402 Fixture Wires 70-241 



ARTICLE 

404 Switches 70-244 

I. Installation 70-244 

II. Construction Specifications 70-247 

406 Receptacles, Cord Connectors, and 

Attachment Plugs (Caps) 70-247 

408 Switchboards and Panelboards 70-250 

I. General 70-250 

II. Switchboards 70-251 

III. Panelboards 70-252 

IV. Construction Specifications 70-253 

410 Luminaires (Lighting Fixtures), 

Lampholders, and Lamps 70-254 

I. General 70-254 

II. Luminaire (Fixture) Locations 70-254 

III. Provisions at Luminaire (Fixture) 

Outlet Boxes, Canopies, and Pans 70-255 

IV. Luminaire (Fixture) Supports 70-256 

V. Grounding 70-257 

VI. Wiring of Luminaires (Fixtures) 70-257 

VII. Construction of Luminaires (Fixtures) 70-259 

VIII. Installation of Lampholders 70-260 

IX. Construction of Lampholders 70-260 

X. Lamps and Auxiliary Equipment 70-260 

XI. Special Provisions for Flush and 

Recessed Luminaires (Fixtures) 70-260 

XII. Construction of Flush and Recessed 

Luminaires (Fixtures) 70-261 

XIII. Special Provisions for 

Electric-Discharge Lighting Systems of 

1000 Volts or Less 70-261 

XIV Special Provisions for 

Electric-Discharge Lighting Systems of 

More Than 1000 Volts 70-262 

XV. Lighting Track 70-263 

411 Lighting Systems Operating at 30 Volts or 

Less 70-264 

422 Appliances 70-264 

I. General 70-264 

II. Installation 70-264 

III. Disconnecting Means 70-267 

IV Construction 70-267 

V Marking 70-268 

424 Fixed Electric Space-Heating Equipment 70-269 

I. General 70-269 

II. Installation 70-269 

III. Control and Protection of Fixed 

Electric Space-Heating Equipment 70-270 

IV Marking of Heating Equipment 70-272 

V Electric Space-Heating Cables 70-272 

VI. Duct Heaters 70-274 

VII. Resistance-Type Boilers 70-274 

VIII. Electrode-Type Boilers 70-275 

IX. Electric Radiant Heating Panels and 

Heating Panel Sets 70-276 

426 Fixed Outdoor Electric Deicing and 

Snow-Melting Equipment 70-278 

1. General 70-278 



2002 Edition 



NATIONAL ELECTRICAL CODE 



CONTENTS 



70-5 



ARTICLE 

II. Installation 70-279 

III. Resistance Heating Elements 70-279 

IV. Impedance Heating 70-280 

V. Skin-Effect Heating 70-280 

VI. Control and Protection 70-281 

427 Fixed Electric Heating Equipment for 

Pipelines and Vessels 70-281 

I. General 70-281 

II. Installation 70-282 

III. Resistance Heating Elements 70-282 

IV. Impedance Heating 70-283 

V Induction Heating 70-283 

VI. Skin-Effect Heating 70-283 

VII. Control and Protection 70-284 

430 Motors, Motor Circuits, and Controllers 70-284 

I. General 70-284 

II. Motor Circuit Conductors 70-290 

III. Motor and Branch-Circuit Overload 

Protection 70-292 

IV. Motor Branch-Circuit Short-Circuit and 
Ground-Fault Protection 70-295 

V Motor Feeder Short-Circuit and 

Ground-Fault Protection 70-298 

VI. Motor Control Circuits 70-299 

VII. Motor Controllers 70-301 

VIII. Motor Control Centers 70-302 

IX. Disconnecting Means 70-304 

X. Over 600 Volts, Nominal 70-307 

XL Protection of Live Parts — All 

Voltages 70-308 

XII. Grounding — All Voltages 70-308 

XIII. Tables 70-309 

440 Air-Conditioning and Refrigerating 

Equipment 70-312 

I. General 70-312 

II. Disconnecting Means 70-3 14 

III. Branch-Circuit Short-Circuit and 

Ground-Fault Protection 70-315 

IV Branch-Circuit Conductors 70-3 1 6 

V. Controllers for Motor-Compressors 70-3 16 

VI. Motor-Compressor and Branch-Circuit 

Overload Protection 70-317 

VII. Provisions for Room Air Conditioners 70-318 

445 Generators 70-319 

450 Transformers and Transformer Vaults 

(Including Secondary Ties) 70-320 

I. General Provisions 70-320 

II. Specific Provisions Applicable to 

Different Types of Transformers 70-324 

III. Transformer Vaults 70-326 

455 Phase Converters 70-327 

I. General 70-327 

II. Specific Provisions Applicable to 

Different Types of Phase Converters 70-328 

460 Capacitors 70-329 

I. 600 Volts, Nominal, and Under 70-329 



ARTICLE 

II. Over 600 Volts, Nominal 70-329 

470 Resistors and Reactors (For Rheostats, 

See 430.82.) 70-330 

I. 600 Volts, Nominal, and Under 70-330 

II. Over 600 Volts, Nominal 70-331 

480 Storage Batteries 70-331 

490 Equipment, Over 600 Volts, Nominal 70-332 

I. General 70-332 

II. Equipment — Specific Provisions 70-332 

III. Equipment — Metal-Enclosed Power 
Switchgear and Industrial Control 

Assemblies 70-335 

IV Mobile and Portable Equipment 70-337 

V. Electrode-Type Boilers 70-337 

Chapter 5 Special Occupancies 

500 Hazardous (Classified) Locations, Classes 

I, II, and III, Divisions 1 and 2 70-339 

501 Class I Locations 70-347 

502 Class II Locations 70-356 

503 Class III Locations 70-362 

504 Intrinsically Safe Systems 70-364 

505 Class I, Zone 0, 1 , and 2 Locations 70-367 

510 Hazardous (Classified) Locations — 

Specific 70-380 

511 Commercial Garages, Repair and Storage 70-380 

513 Aircraft Hangars 70-382 

5 14 Motor Fuel Dispensing Facilities 70-385 

515 Bulk Storage Plants 70-389 

516 Spray Application, Dipping, and Coating 

Processes 70-393 

517 Health Care Facilities 70-399 

I. General 70-399 

II. Wiring and Protection 70^102 

III. Essential Electrical System 70-405 

IV. Inhalation Anesthetizing Locations 70-4 1 1 

V. X-Ray Installations , 70-414 

VI. Communications, Signaling Systems, 
Data Systems, Fire Alarm Systems, and 

Systems Less Than 120 Volts, Nominal 70-415 

VII. Isolated Power Systems 70-416 

518 Places of Assembly 70-417 

520 Theaters, Audience Areas of Motion 
Picture and Television Studios, 
Performance Areas, and Similar Locations 70-418 

I. General 70^118 

II. Fixed Stage Switchboards 70-419 



NATIONAL ELECTRICAL CODE 



2002 Edition 



70-6 



CONTENTS 



ARTICLE 

III. Fixed Stage Equipment Other Than 
Switchboards 70-421 

IV. Portable Switchboards on Stage 70-422 

V. Portable Stage Equipment Other Than 

Switchboards 70-425 

VI. Dressing Rooms 70^126 

VII. Grounding 70-426 

525 Carnivals, Circuses, Fairs, and Similar 

Events 70-427 

I. General Requirements 70^-27 

II. Power Sources 70-427 

III. Wiring Methods 70^27 

IV. Grounding and Bonding 70^128 

527 Temporary Installations 70^129 

530 Motion Picture and Television Studios 

and Similar Locations 70-430 

I. General 70^130 

II. Stage or Set 70-431 

III. Dressing Rooms 70^133 

IV Viewing, Cutting, and Patching Tables 70^34 

V Cellulose Nitrate Film Storage Vaults 70-434 

VI. Substations 70^434 

540 Motion Picture Projection Rooms 70^134 

I. General 70-434 

II. Equipment and Projectors of the 

Professional Type 70-434 

III. Nonprofessional Projectors 70-435 

IV Audio Signal Processing, Amplification, 

and Reproduction Equipment 70^135 

545 Manufactured Buildings 70^436 

547 Agricultural Buildings 70-437 

550 Mobile Homes, Manufactured Homes, and 

Mobile Home Parks 70-439 

I. General 70^139 

II. Mobile and Manufactured Homes 70^140 

III. Services and Feeders 70-447 

551 Recreational Vehicles and Recreational 

Vehicle Parks 70^149 

I. General 70-449 

II. Low- Voltage Systems 70^450 

III. Combination Electrical Systems 70-452 

IV Other Power Sources 70^152 

V. Nominal 120- Volt or 120/240-Volt 

Systems 70-453 

VI. Factory Tests 70^160 

VII. Recreational Vehicle Parks 70^160 

552 Park Trailers 70^163 

I. General 70^63 

II. Low-Voltage Systems 70^163 

III. Combination Electrical Systems 70^64 

IV Nominal 120- Volt or 120/240-Volt 

Systems 70-465 

V. Factory Tests 70^172 



ARTICLE 

553 Floating Buildings 70^172 

I. General 70-472 

II. Services and Feeders 70—472 

III. Grounding 70-472 

555 Marinas and Boatyards 70^173 

Chapter 6 Special Equipment 

600 Electric Signs and Outline Lighting 70^177 

I. General 70-477 

II. Field-Installed Skeleton Tubing 70-480 

604 Manufactured Wiring Systems 70-48 1 

605 Office Furnishings (Consisting of Lighting 
Accessories and Wired Partitions) 70-482 

610 Cranes and Hoists 70-483 

I. General 70-483 

II. Wiring 70^183 

III. Contact Conductors 70^186 

IV Disconnecting Means 70-487 

V Overcurrent Protection 70-487 

VI. Control 70-488 

VII. Grounding 70-488 

620 Elevators, Dumbwaiters, Escalators, 
Moving Walks, Wheelchair Lifts, and 

Stairway Chair Lifts 70-488 

I. General 70-488 

II. Conductors 70^190 

III. Wiring 70^191 

IV Installation of Conductors 70-494 

V Traveling Cables 70^194 

VI. Disconnecting Means and Control 70-495 

VII. Overcurrent Protection 70-496 

VIII. Machine Rooms, Control Rooms, 

Machinery Spaces, and Control Spaces 70—497 

IX. Grounding 70^197 

X. Emergency and Standby Power 

Systems 70-497 

625 Electric Vehicle Charging System 70-498 

I. General 70-498 

II. Wiring Methods 70^198 

III. Equipment Construction 70-499 

IV. Control and Protection 70-499 

V Electric Vehicle Supply Equipment 

Locations 70-500 

630 Electric Welders 70-502 

I. General 70-502 

II. Arc Welders 70-502 

III. Resistance Welders 70-503 

IV. Welding Cable 70-504 

640 Audio Signal Processing, Amplification, 

and Reproduction Equipment 70-504 

I. General 70-504 

II. Permanent Audio System Installations 70-507 



2002 Edition 



NATIONAL ELECTRICAL CODE 



CONTENTS 



70-7 



ARTICLE 

III. Portable and Temporary Audio System 

Installations 70-508 

645 Information Technology Equipment 70-509 

647 Sensitive Electronic Equipment 70-5 1 1 

650 Pipe Organs 70-512 

660 X-Ray Equipment 70-513 

I. General 70-513 

II. Control 70-514 

III. Transformers and Capacitors 70-5 1 4 

IV. Guarding and Grounding 70-5 14 

665 Induction and Dielectric Heating 

Equipment 70-5 15 

I. General 70-515 

II. Guarding, Grounding, and Labeling 70-516 

668 Electrolytic Cells 70-516 

669 Electroplating 70-519 

670 Industrial Machinery 70-520 

675 Electrically Driven or Controlled 

Irrigation Machines 70-521 

I. General 70-521 

II. Center Pivot Irrigation Machines 70-523 

680 Swimming Pools, Fountains, and Similar 

Installations 70-523 

I. General 70-523 

II. Permanently Installed Pools 70-526 

III. Storable Pools 70-532 

IV. Spas and Hot Tubs 70-533 

V. Fountains 70-535 

VI. Pools and Tubs for Therapeutic Use 70-536 

VII. Hydromassage Bathtubs 70-537 

685 Integrated Electrical Systems 70-537 

I. General 70-537 

II. Orderly Shutdown 70-538 

690 Solar Photovoltaic Systems 70-538 

I. General 70-538 

II. Circuit Requirements 70-540 

III. Disconnecting Means 70-542 

IV Wiring Methods 70-543 

V Grounding 70-544 

VI. Marking 70-545 

VII. Connection to Other Sources 70-545 

VIII. Storage Batteries 70-546 

IX. Systems Over 600 Volts 70-547 

692 Fuel Cell Systems 70-547 

I. General 70-547 

II. Circuit Requirements 70-548 

III. Disconnecting Means 70-549 

IV. Wiring Methods 70-549 

V Grounding 70-549 

VI. Marking 70-549 

VII. Connection to Other Circuits 70-549 



ARTICLE 

VIII. Outputs Over 600 Volts 70-550 

695 Fire Pumps 70-550 

Chapter 7 Special Conditions 

700 Emergency Systems 70-555 

I. General 70-555 

II. Circuit Wiring 70-556 

III. Sources of Power 70-557 

IV Emergency System Circuits for 

Lighting and Power 70-558 

V Control — Emergency Lighting 

Circuits 70-559 

VI. Overcurrent Protection 70-559 

701 Legally Required Standby Systems 70-559 

I. General 70-559 

II. Circuit Wiring 70-560 

III. Sources of Power 70-561 

IV Overcurrent Protection 70-562 

702 Optional Standby Systems 70-562 

I. General 70-562 

II. Circuit Wiring 70-563 

III. Grounding 70-563 

705 Interconnected Electric Power Production 

Sources 70-563 

720 Circuits and Equipment Operating at Less 

Than 50 Volts 70-565 

725 Class 1, Class 2, and Class 3 

Remote-Control, Signaling, and 

Power-Limited Circuits 70-565 

I. General 70-565 

II. Class 1 Circuits 70-566 

III. Class 2 and Class 3 Circuits 70-568 

727 Instrumentation Tray Cable: Type ITC 70-574 

760 Fire Alarm Systems 70-575 

I General 70-575 

II. Non-Power-Limited Fire Alarm 

(NPLFA) Circuits 70-576 

III. Power-Limited Fire Alarm (PLFA) 

Circuits 70-579 

770 Optical Fiber Cables and Raceways 70-583 

I. General 70-583 

II. Protection 70-584 

III. Cables Within Buildings 70-584 

780 Closed-Loop and Programmed Power 

Distribution 70-587 

Chapter 8 Communications Systems 

800 Communications Circuits 70-589 

I. General 70-589 

II. Conductors Outside and Entering 

Buildings 70-590 



NATIONAL ELECTRICAL CODE 



2002 Edition 



70-8 



CONTENTS 



ARTICLE 

III. Protection 70-591 

IV. Grounding Methods 70-592 

V. Communications Wires and Cables 

Within Buildings 70-593 

810 Radio and Television Equipment 70-597 

I. General 70-597 

II. Receiving Equipment — Antenna 

Systems 70-598 

III. Amateur Transmitting and Receiving 

Stations — Antenna Systems 70-600 

IV. Interior Installation — Transmitting 

Stations 70-601 

820 Community Antenna Television and Radio 

Distribution Systems 70-601 

I. General 70-601 

II. Cables Outside and Entering Buildings 70-602 

III. Protection 70-603 

IV. Grounding Methods 70-603 

V. Cables Within Buildings 70-604 

830 Network-Powered Broadband 

Communications Systems 70-607 

I. General 70-607 

II. Cables Outside and Entering Buildings 70-609 

III. Protection 70-612 

IV. Grounding Methods 70-613 

V Wiring Methods Within Buildings 70-614 

TABLES 

Chapter 9 Tables 

1 Percent of Cross Section of Conduit and 

Tubing for Conductors 70-617 



TABLES 
4 



5A 



11(A) 
1KB) 
12(A) 
12(B) 



Dimensions and Percent Area of Conduit 
and Tubing (Areas of Conduit or Tubing 
for the Combinations of Wires Permitted 
in Table 1, Chapter 9) 70-617 

Dimensions of Insulated Conductors and 

Fixture Wires 70-622 

Compact Aluminum Building Wire 

Nominal Dimensions* and Areas 70-624 

Conductor Properties 70-625 

Alternating-Current Resistance and 

Reactance for 600- Volt Cables, 3-Phase, 

60 Hz, 75°C (167°F) — Three Single 

Conductors in Conduit 70-626 

Class 2 and Class 3 Alternating-Current 

Power Source Limitations 70-628 

Class 2 and Class 3 Direct-Current Power 

Source Limitations 70-628 

PLEA Alternating-Current Power Source 

Limitations 70-629 

PLFA Direct-Current Power Source 

Limitations 70-629 

AnnexA 70-631 

Annex B 70-635 

AnnexC 70-645 

Annex D 70-667 

AnnexE 70-675 

AnnexF 70-677 

Index 70-681 



2002 Edition 



NATIONAL ELECTRICAL CODE 



NATIONAL ELECTRICAL CODE COMMITTEE 



70-9 



NATIONAL ELECTRICAL CODE COMMITTEE 



These lists represent the membership at the time each Committee was balloted on the text of this edition. Since that 
time, changes in the membership may have occurred. A key to classifications is found at the back of this book. 

Technical Correlating Committee 

D. Harold Ware, Chair [IM] 

Libra Electric Co., OK 

Rep. National Electrical Contractors Association 

Mark W. Earley, Secretary 

National Fire Protection Association, MA 

(nonvoting) 

Jean A. O'Connor, Recording Secretary 

National Fire Protection Association, MA 

(nonvoting) 



Richard Berman, Underwriters Laboratories Inc., IL [RT] 
James E. Brunssen, Telcordia Technologies, Inc., NJ [UT] 

Rep. Alliance for Telecommunications Industry Solutions 
Michael I. Callanan, Nat'l. Joint Apprentice & Training 
Committee, PA [L] 

Rep. International Brotherhood of Electrical Workers 
Philip H. Cox, IntT. Association of Electrical Inspectors, TX [E] 

Rep. International Association of Electrical Inspectors 
William R. Drake, Marinco, CA [M] 
Antonio Macias, AMERIC DF, Mexico [U] 
James T. Pauley, Square D Co., KY [M] 

Rep. National Electrical Manufacturers Association 
Joseph E. Pipkin, U.S. Dept. of Labor OSHA, DC [E] 
John W. Troglia, Edison Electric Institute, WI [UT] 

Rep. Edison Electric Institute 
Craig M. Wellman, DuPont Engineering, DE [U] 

Rep. American Chemistry Council 

Alternates 
Jeffrey Boksiner, Telcordia Technologies, Inc., NJ [UT] 
Rep. Alliance for Telecommunications Industry Solutions 
(Alt. to J. E. Brunssen) 



James M. Daly, General Cable, NY [M] 

Rep. National Electrical Manufacturers Association 

(Alt. to J. T. Pauley) 
John R. Kovacik, Underwriters Laboratories, IL [RT] 

(Alt. to R. Berman) 
Edward C. Lawry, WI [E] 

Rep. International Association of Electrical Inspectors 

(Alt. to P. H. Cox) 
William M. Lewis, Eli Lilly & Co., IN [U]Rep. American 
Chemistry Council 

(Alt. to C. M. Wellman) 
Neil F. LaBrake, Jr., Niagara Mohawk Power Corp., NY [UT] 

Rep. Edison Electric Institute 

(Alt. to J. W. Troglia) 
Michael D. Toman, MEGA Power Electrical Services, Inc., MD 
[IM] 

Rep. National Electrical Contractors Association 

(Alt. To D. H. Ware) 

Nonvoting 

Richard G. Biermann, Biermann Electric Co. Inc., IA 
(Member Emeritus) 



CODE-MAKING PANEL NO. 1 

Articles 90, 100, 110 

John D. Minick, Chair 

Nat'l. Electrical Manufacturers Assn., TX [M] 

Rep. National Electrical Manufacturers Association 



Michael A. Anthony, University of Michigan, MI [U] 

Rep. The Association of Higher Education Facilities Officers 
Philip H. Cox, IntT. Association of Electrical Inspectors, TX [E] 

Rep. International Association of Electrical Inspectors 
David A. Dini, Underwriters Laboratories Inc. IL [RT] 
William T. Fiske, Intertek Testing Services N.A. Inc., NY [RT] 
H. Landis Floyd, II, The DuPont Company, DE [U] 

Rep. Institute of Electrical & Electronics Engineers, Inc. 
David L. Hittinger, IEC of Greater Cincinnati, OH [IM] 

Rep. Independent Electrical Contractors, Inc. 
Don B. Ivory, Idaho Electrical JATC, ID [L] 

Rep. International Brotherhood of Electrical Workers 
Antonio Macias, AMERIC DF, Mexico [U] 
Randall R. McCarver, Telcordia Technologies, Inc., NJ [UT] 

Rep. Alliance for Telecommunications Industry Solutions 
Ralph C. Prichard, Hercules, Inc., DE [U] 

Rep. American Chemistry Council 



H. Brooke Stauffer, Nat'l. Electrical Contractors Assn., MD 
[IM] 

Rep. National Electrical Contractors Association 
John W. Troglia, Edison Electric Institute, WI [UT] 
Rep. Edison Electric Institute 

Alternates 
Louis A. Barrios, Jr., Equilon Enterprises, LLC, TX [U] 

Rep. American Chemistry Council 

(Alt. To R. C. Prichard) 
David P. Brown, Baltimore Gas & Electric Co., MD [UT] 

Rep. Edison Electric Institute 

(Alt. to J. W. Troglia) 
Timothy Lee Emory, Emory Electric, Inc., NC [IM] 

Rep. Independent Electrical Contractors, Inc. 

(Alt. to D. L. Hittinger) 
Russell J. Helmick, Jr., City of Irvine, CA [E] 



NATIONAL ELECTRICAL CODE 



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NATIONAL ELECTRICAL CODE COMMITTEE 



Rep. International Association of Electrical Inspectors 

(Alt. to P. H. Cox) 
Mahbub Hoque, Telcordia Technologies, NJ [UT] 

Rep. Alliance for Telecommunications Industry Solutions 

(Alt. to R. R. McCarver) 
Donald H. McCullough, II, Westinghouse Savannah River Co., 
SC [U] 

Rep. Institute of Electrical & Electronics Engineers, Inc. 

(Alt. to H. L. Floyd, II) 
Larry Miller, Nat'l. Electrical Manufacturers Assn., VA [M] 

Rep. National Electrical Manufacturers Association 

(Alt. to J. D. Minick) 



Ricky L. Oakland, IBEW, WY [L] 

Rep. International Brotherhood of Electrical Workers 

(Alt. to D. B. Ivory) 
William L. Schallhammer, Underwriters Laboratories, Inc. 
[RT] 

(Alt. to D. A. Dini) 

Nonvoting 
Ark Tsisserev, City of Vancouver, BC 

Rep. Canadian Standards Association International 
William Wusinich, U.S. Dept of Labor, PA [E] 



IL 



CODE-MAKING PANEL NO. 2 

Articles 210, 215, 220, Chapter 9, Annex D 
Examples 1 through 6 

James W. Carpenter, Chair 

North Carolina Dept. of Insurance, NC [E] 
Rep. International Association of Electrical Inspectors 



Richard W. Becker, Engineered Electrical Systems, Inc., WA [U] 

Rep. Institute of Electrical & Electronics Engineers, Inc. 
Thomas L. Harman, University of Houston/Clear Lake, TX [SE] 
Bernard Mericle, IBEW, Local Union 236, NY [L] 

Rep. International Brotherhood of Electrical Workers 
Robert E. Moore, TECO Energy, FL [UT] 

Rep. Edison Electric Institute 
Donald A. Nissen, Underwriters Laboratories, Inc., IL [RT] 
James T. Pauley, Square D Co., KY [M] 

Rep. National Electrical Manufacturers Association 
Joseph Patterson Roche, Celanese Acetate, SC [U] 

Rep. American Chemistry Council 
Albert F. Sidhom, U.S. Army Corps of Engineers, CA [U] 
Michael D. Toman, MEGA Power Electrical Services, Inc., MD 
[IM] 

Rep. National Electrical Contractors Association 
Robert G. Wilkinson, Independent Electrical Contractors of 
Houston, Inc., TX [IM] 

Rep. Independent Electrical Contractors, Inc. 

Alternates 

Ernest S. Broome, City of Knoxville, TN [E] 

Rep. International Association of Electrical Inspectors 

(Alt. to J. W. Carpenter) 
Charles G. Crawford, TXU Electric, TX [UT] 

Rep. Edison Electric Institute 

(Alt. to R. E. Moore) 



Ernie Howell, IEC, Rocky Mountain Chapter, CO [IM] 

Rep. Independent Electrical Contractors 

(Alt. to R. G. Wilkinson) 
James R. Jones, University of Alabama at Birmingham, AL [U] 

Rep. Institute of Electrical & Electronics Engineers, Inc. 

(Alt. to R. W. Becker) 
Daniel J. Kissane, Pass & Seymour/Legrand, NY [M] 

Rep. National Electrical Manufacturers Association 

(Alt. to J. T. Pauley) 
Charles D. Marshall, Jr., IBEW Local 948, MI [L] 

Rep. International Brotherhood of Electrical Workers 

(Alt. to B. Mericle) 
Susan W. Porter, Underwriters Laboratories Inc., NY [RT] 

(Alt. to D. A. Nissen) 
J. Morris Trimmer, University of Florida, FL [SE] 

(Alt. to T. L. Harman) 
Joseph E. Wiehagen, Nat'l. Assn. of Home Builders, MD [IM] 

Rep. National Association of Home Builders 

(Voting Alt. to NAHB Rep.) 

Nonvoting 

Douglas A. Lee, U.S. Consumer Product Safety Commission, MD 
Andrew M. Trotta, U.S. Consumer Product Safety Commission, 
MD 



CODE-MAKING PANEL NO. 3 
Articles 300, 527, 690, 692 

Raymond W. Weber, Chair 
Dept. of Commerce, WI [E] 
Rep. International Association of Electrical Inspectors 



Joseph J. Andrews, Electrical Safety Resources, Inc., SC [U] 

Rep. Institute of Electrical & Electronics Engineers, Inc. 
Charles W. Beile, Allied Tube & Conduit/Tyco, IL [M] 

Rep. National Electrical Manufacturers Association 
Ward I. Bower, Sandia Nat'l. Laboratories, NM [U] 

Rep. Solar Energy Industries Association 

(VL 690) 
Paul Casparro, Scranton Electricians JATC, PA [L] 

Rep. International Brotherhood of Electrical Workers 



Charles W. Forsberg, OH [M] 

Rep. Society of the Plastics Industry Inc. 
Jack A. Gruber, Wheatland Tube Co., PA [M] 

Rep. American Iron and Steel Institute 
Dennis B. Horman, PacifiCorp, UT [UT] 

Rep. Edison Electric Institute 
Kenneth Krastins, Plug Power, Inc., NY [M] 

Rep. US Fuel Cell Council 

(VL691) 



2002 Edition 



NATIONAL ELECTRICAL CODE 



NATIONAL ELECTRICAL CODE COMMITTEE 



70-11 



George M. Kreiner, Underwriters Laboratories Inc., IL [RT] 
Ronald E. Maassen, Lemberg Electric Co., Inc., WI [IM] 

Rep. National Electrical Contractors Association 
Steven J. Owen, AL [IM] 

Rep. Associated Builders and Contractors, Inc. 
David A. Pace, Olin Corporation, AL [U] 

Rep. American Chemistry Council 

Alternates 

Martin J. Brett, Jr., Wheatland Tube Co., NJ [M] 

Rep. American Iron and Steel Institute 

(Alt. toJ.A.Gruber) 
Les Easter, Allied Tube and Conduit, IL [M] 

Rep. National Electrical Manufacturers Association 

(Alt. to C. W. Beile) 
James D. Erwin, Celanese, Ltd., TX [U] 

Rep. American Chemistry Council 

(Alt. to D. A. Pace) 
Palmer L. Hickman, IBEW Local 380, PA [L] 

Rep. International Brotherhood of Electrical Workers 

(Alt. to P. Casparro) 
David H. Kendall, Carlon, Lamson & Sessions, OH [M] 



Rep. Society of the Plastics Industry Inc. 

(Alt.toC.W.Forsberg) 
Mark C. Ode, Underwriters Laboratories, Inc., NC [RT] 

(Alt. to G.M. Kreiner) 
Richard P. Owen, City of St. Paul, MN [E] 

Rep. International Association of Electrical Inspectors 

(Alt. to R. W. Weber) 
Roger S. Passmore, Davis Electrical Constructors, Inc., SC 
[IM] 

Rep. Associated Builders and Contractors, Inc. 

(Alt. to S.J. Owen) 
George E. Richey, Consumers Energy, MI [UT] 

Rep. Edison Electric Institute 

(Alt. toD.B.Horman) 
Melvin K. Sanders, Things Electrical Co., Inc. dba (TECo., Inc), IA 
[U] 

Rep. Institute of Electrical & Electronics Engineers, Inc. 

(Alt. to J. J. Andrews) 
Robert H. Wills, Advanced Energy Systems Inc., NH [U] 

Rep. Solar Energy Industries Association 

(VL 690) 

(Alt. to W. I. Bower) 



CODE-MAKING PANEL NO. 4 

Articles 225, 230 

C.John Beck, Chair [UT] 

Pacific Gas and Electric Co., CA 

Rep. Edison Electric Institute 



Malcolm Allison, Ferraz Shawmut, MA [M] 

K. W. Carrick, Electrical Engineering Professional Services, 

Inc., MS [U] 

Rep. Institute of Electrical & Electronics Engineers, Inc. 
Floyd C. Ferris, New York Board of Fire Underwriters, NY 
Howard D. Hughes, Hughes Electric Co. Inc., AR [IM] 

Rep. National Electrical Contractors Association 
William M. Lewis, Eli Lilly & Co., IN [U] 

Rep. American Chemistry Council 
Junior L. O wings, State of Oregon, OR [E] 

Rep. International Association of Electrical Inspectors 
Robert J. Pollock, Underwriters Laboratories Inc., IL, RT 
Mark H. Sumrall, IBEW Local 527, TX [L] 

Rep. International Brotherhood of Electrical Workers 
John W. Young, Siemens Energy & Automation, Inc., GA 

Rep. National Electrical Manufacturers Association 
Vincent Zinnante, Advantage Electric, Inc., TX [IM] 

Rep. Independent Electrical Contractors, Inc. 

Alternates 

Thomas L. Adams, Exelon Corporation, IL [UT] 
Rep. Edison Electric Institute 
(Alt. to C.J. Beck) 



Terry D. Cole, Hamer Electric/Associated Electrical 
Consultants, Inc., WA [IM] 

Rep. Independent Electrical Contractors, Inc. 

(Alt. to V. Zinnante) 
[E] Dennis Darling, Ayres , Lewis , Norri s , & May, Inc . , MI [U] 

Rep. Institute of Electrical & Electronics Engineers, Inc. 

(Alt. to K. W. Carrick) 
Timothy Owens, City of San Diego, CA [E] 

Rep. International Association of Electrical Inspectors 

(Alt. to J. L. O wings) 
Philip M. Piqueira, General Electric Co., CT [M] 

Rep. National Electrical Manufacturers Association 

(Alt. to J. W.Young) 
John A. Sigmund, PPG Industries, Inc., LA [U] 
[M] Rep. American Chemistry Council 

(Alt. to W.M.Lewis) 
William J. Tipton, IBEW, OH [L] 

Rep. International Brotherhood of Electrical Workers 

(Alt. to M.H. Sumrall) 



CODE-MAKING PANEL NO. 5 
Articles 200, 250, 280, 285 

Ronald J. Toomer, Chair [IM] 

Toomer Electrical Co. Inc., LA 

Rep. National Electrical Contractors Association 



Jeffrey Boksiner, Telcordia Technologies, Inc., NJ [UT] 
Rep. Alliance for Telecommunications Industry Solutions 

David T. Brender, Copper Development Association, Inc., NY 

[M] 

Rep. Copper Development Association Inc. 



Martin J. Brett, Jr., Wheatland Tube Co., NJ [M] 

Rep. American Iron and Steel Institute 
Elio L. Checca, U.S . Dept. of Labor, VA [E] 
Paul Dobrowsky, Eastman Kodak Co., NY [U] 
Rep. American Chemistry Council 



NATIONAL ELECTRICAL CODE ' 



2002 Edition 



70-12 



NATIONAL ELECTRICAL CODE COMMITTEE 



Gerald L. Hadeen, Alflex Corp., CA [M] 

Rep. The Aluminum Association 
Dan Hammel, Int'l. Brotherhood of Electrical Workers, IA [L] 

Rep. International Brotherhood of Electrical Workers 
Michael J. Johnston, Int'l. Association of Electrical Inspectors, 
Inc.,TX [E] 

Rep. International Association of Electrical Inspectors 
Charles F. Mello, Electro-Test, Inc., OR [IM] 

Rep. International Electrical Testing Association Inc. 
Elliot Rappaport, Electro Technology Consultants, Inc., MI [U] 

Rep. Institute of Electrical & Electronics Engineers, Inc. 
Ted G. Robertson, Robertson Electric, Inc., TX, [IM] 

Rep. Independent Electrical Contractors, Inc. 
Walter Skuggevig, Underwriters Laboratories, Inc., NY [RT] 
Gregory J. Steinman, Thomas & Betts Corp., TN [M] 

Rep. National Electrical Manufacturers Association 
Robert G. Stoll, Thomas Associates, Inc., OH [M] 

Rep. Power Tool Institute, Inc. 
C. Douglas White, Reliant Energy, TX [UT] 

Rep. Edison Electric Institute 

Alternates 

Martin D. Adams, Adams Electric, Inc., CO [IM] 

Rep. National Electrical Contractors Association 

(Alt. to R. J. Toomer) 
David A. Dini, Underwriters Laboratories Inc, IL [RT] 

(Alt. to W. Skuggevig) 
Timothy Edwards, Alcan Cable Co., GA [M] 

Rep. The Aluminum Association 

(Alt. to G. L. Hadeen) 



Garfield B. Gwyn, Gwyn Electrical & Plumbing Co., NC [IM] 

Rep. Independent Electrical Contractors, Inc. 

(Alt. to T. G. Robertson) 
Ronald Lai, FCI Electrical, NH [M] 

Rep. National Electrical Manufacturers Association 

(Alt. to G. J. Steinman) 
Dennis E. Lammert, Ameren Services, MO [UT] 

Rep. Edison Electric Institute 

(Alt. to C. D. White) 
Richard E. Loyd, R&N Associates, AR [M] 

Rep. American Iron and Steel Institute 

(Alt. to M. J. Brett, Jr.) 
Daleep C. Mohla, Union Carbide Corp., TX [U] 

Rep. Institute of Electrical & Electronics Engineers, Inc. 

(Alt. to E. Rappaport) 
Thomas E.Moore, City of Norton, OH [E] 

Rep. International Association of Electrical Inspectors 

(Alt. to M. J. Johnston) 
David Peot, Ryobi, SC [M] 

Rep. Power Tool Institute, Inc. 

(Alt. to R. G. Stroll) 
Thomas J. Shea, IBEW Local 405, IA [L] 

Rep. International Brotherhood of Electrical Workers 

(Alt. to D. Hammel) 
J. Philip Simmons, Simmons Electrical Services, WA [M] 

(Alt. to D. T. Brender) 
Michael K. Toney, Equistar Chemicals, LP, TX [U] 

Rep. American Chemistry Council 

(Alt. to P. Dobrowsky) 



CODE-MAKING PANEL NO. 6 
Articles 310, 400, 402, Chapter 9 Tables 5 through 9 

Stephen J. Thorwegen, Jr., Chair [IM] 

Fisk Electric Co., TX 

Rep. National Electrical Contractors Association 



Julian R. Burns, Burns Electrical Contractors, Inc., NC [IM] 

Rep. Independent Electrical Contractors, Inc. 
William C. Ferrell, IBEW, OH [L] 

Rep. International Brotherhood of Electrical Workers 
Samuel B. Friedman, BICC General, RI [M] 

Rep. National Electrical Manufacturers Association 
Steven Galan, Underwriters Laboratories Inc., NY [RT] 
Ravindra H. Ganatra, Alcan Cable, GA [M] 

Rep. The Aluminum Association 
David G. Komassa, Wisconsin Electric Power Co., WI [UT] 

Rep. Edison Electric Institute 
L. Bruce McClung, Union Carbide Corp., WV [U] 

Rep. Institute of Electrical & Electronics Engineers, Inc. 
Dale W. Pettigrew, Cognis Corp., OH [U] 

Rep. American Chemistry Council 
Oran P. Post, City of Cuyahoga Falls, OH [E] 

Rep. International Association of Electrical Inspectors 
Joseph Zimnoch, The Okonite Company, NJ [M] 

Rep. Copper Development Association Inc. 

Alternates 

Kenneth L. Brotherton, IBEW Local 683, OH [L] 

Rep. International Brotherhood of Electrical Workers 

(Alt. to W.C. Ferrell) 
James M. Daly, General Cable, NY [M] 

Rep. Copper Development Association, Inc. 

(Alt. to J. Zimnoch) 



G. W. "Jerry" Kent, Kent Electric Systems, TX [IM] 

Rep. Independent Electrical Contractors 

(Alt. to J. R. Burns) 
Danny P. Liggett, DuPont Engineering, DE [U] 

Rep. American Chemistry Council 

(Alt. to D. W. Pettigrew) 
Lowell S. Lisker, American Insulated Wire Corp., RI [M] 

Rep. National Electrical Manufacturers Association 

(Alt. to S.B.Friedman) 
Harry J. Sassaman, Forest Electric Corp., NJ [IM] 

Rep. National Electrical Contractors Association 

(Alt. to S. J. Thorwegen, Jr.) 
JohnStacey, City of St Louis, MO [E] 

Rep. International Association of Electrical Inspectors 

(Alt. to O. P. Post) 
Fred Truban, American Electric Power, OH [UT] 

Rep. Edison Electric Institute 

(Alt. to D. G. Komassa) 
Donald A. Voltz, Mustang Engineering, Inc., TX [U] 

Rep. Institute of Electrical & Electronics Engineers, Inc. 

(Alt. to L.B. McClung) 
Austin D. Wetherell, Underwriters Laboratories Inc., NY [RT] 

(Alt. to S. Galan) 



2002 Edition 



NATIONAL ELECTRICAL CODE 



NATIONAL ELECTRICAL CODE COMMITTEE 



70-13 



CODE-MAKING PANEL NO. 7 

Articles 320, 322, 324, 326, 328, 330, 332, 334, 336, 338, 340, 382, 394, 396, 398 

Thomas E. Trainor, Chair 
City of San Diego, CA [E] 
Rep. International Association of Electrical Inspectors 



James M. Daly, General Cable, NY [M] 

Rep. National Electrical Manufacturers Association 
Brian Ensign, Intertek Testing Services, N.A. Inc., NY [RT] 
Chris Fahrenthold, MH Technologies, TX [IM] 

Rep. Independent Electrical Contractors, Inc. 
Robert L. Gotham, Rose City Electric Co., Inc., OR [IM] 

Rep. National Electrical Contractors Association 
Thomas J. Guida, Underwriters Laboratories Inc., NY [RT] 
Ronald G. Nickson, NatT. Multi Housing Council, DC [U] 

Rep. National Multi Housing Council 
Bruce W. Nutt, TXU Electric & Gas, TX [UT] 

Rep. Edison Electric Institute 
John E. Propst, Equilon Enterprises LLC, TX [U] 

Rep. American Chemistry Concil 
Thomas G. Rodgers, Dickens & Assoc. Inc., FL [L] 

Rep. International Brotherhood of Electrical Workers 
David E. Schumacher, All County Electric Co., IA [IM] 

Rep. Associated Builders and Contractors, Inc. 
H. R. Stewart, HRS Consulting, TX [U] 

Rep. Institute of Electrical & Electronics Engineers, Inc. 
George A. Straniero, AFC Cable Systems, Inc., NJ [M] 

Rep. Copper Development Association Inc. 
Robert S. Strength, Product Safety Management Inc., FL [M] 

Rep. Society of the Plastics Industry Inc. 
Richard Temblador, Alflex Corporation, CA [M] 

Rep. The Aluminum Association 

Alternates 

Harry C. Brown, IBEW Local 606, FL [L] 

Rep. International Brotherhood of Electrical Workers 
(Alt. to T. G. Rodgers) 



Arthur Buxbaum, San Diego Building Inspection Dept., CA [E] 

Rep. International Association of Electrical Inspectors 

(Alt. to T. E. Trainor) 
John J. Cangemi, Underwriters Laboratories, Inc., NY [RT] 

(Alt. to T. J. Guida) 
James V. Fitzgerald, The Okonite Co., NJ [M] 

Rep. National Electrical Manufacturers Association 

(Alt. to J. M. Daly) 
Ravindra H. Ganatra, Alcan Cable, GA [M] 

Rep. The Aluminum Association 

(Alt. to R. Temblador) 
Herman J. Hall, TX [M] 

Rep. Society of the Plastics Industry Inc. 

(Alt. to R. S. Strength) 
Greg Hall, Better- Way Electric, Inc., CO [IM] 

Rep. Independent Electrical Contractors, Inc. 

(Alt. to C. Fahrenthold) 
Dennis A. Nielsen, Southdown, Inc., CA [U] 

Rep. Institute of Electrical & Electronics Engineers, Inc. 

(Alt. to H. R. Stewart) 
John Thomas Thompson, A. B.C. Marathon Electrical Co., Inc., 
AL [IM] 

Rep. Associated Builders and Contractors, Inc. 

Alt. to D. E. Schumacher) 
David B. West, Duke Energy Inc., NC [UT] 

Rep. Edison Electric Institute 

(Alt. to B. W. Nutt) 
Thomas H. Wood, Cecil B. Wood Inc., IL [IM] 

Rep. National Electrical Contractors Association 

(Alt. to R. L. Gotham) 



• 



CODE-MAKING PANEL NO. 8 

Articles 342, 344, 348, 350, 352, 354, 356, 358, 360, 362, 366, 368, 370, 372, 374, 376, 378, 380, 384, 386, 388, 390, 392 

Chapter 9 Tables 1 through 4, and Appendix C 

Kenneth E. Jannot, Chair [UT] 

Detroit Edison, MI 

Rep. Edison Electric Institute 



Richard Berman, Underwriters Laboratories Inc., IL [RT] 
John S. Corry, Corry Electric Inc., CA [IM] 

Rep. Associated Builders and Contractors, Inc. 
Robert W. Cox, Astra Zeneca, DE [U] 

Rep. American Chemistry Council 
George R. Dauberger, Thomas & Betts Corporation, TN [M] 

Rep. National Electrical Manufacturers Association 
James C. Dollins, AFC Cable Systems, MA [M] 

Rep. The Aluminum Association 
M. Shan Griffith, Brown & Root, Inc., TX [U] 

Rep. Institute of Electrical & Electronics Engineers, Inc. 
David H. Kendall, Carlon, Lamson & Sessions, OH [M] 

Rep. Society of the Plastics Industry Inc. 
Wayne A. Lilly, City of Harrisonburg, VA [E] 

Rep. International Association of Electrical Inspectors 
Richard E. Loyd, R&N Associates, AR [M] 

Rep. American Iron and Steel Institute 



Stephen P. Poholski, Newkirk Electric Associates, Inc., MI [IM] 

Rep. National Electrical Contractors Association 
C. Ernest Reynolds, Hatfield-Reynolds Electric Co., AZ [IM] 

Rep. Independent Electrical Contractors, Inc. 
Dennis L. Rowe, NY Board of Fire Underwriters, NY [E] 

Rep. New York Board of Fire Underwriters 
Ray R. Simpson, IntT. Brotherhood of Electrical Workers, IN 
[L] 

Rep. International Brotherhood of Electrical Workers 

Alternates 

Jimmy R. Bonds, Oklahoma State Dept of Health, OK [E] 

Rep. International Association of Electrical Inspectors 

(Alt. to W. A. Lilly) 
Kenneth E. Christ, Solutie, Inc., MO [U] 

Rep. American Chemistry Council 

(Alt. to R. W. Cox) 



NATIONAL ELECTRICAL CODE 



2002 Edition 



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NATIONAL ELECTRICAL CODE COMMITTEE 



Joseph G. Dabe, City of St. Paul, MN [L] 

Rep. International Brotherhood of Electrical Workers 

(Alt. to R. R. Simpson) 
Ron Duren, PacifiCorp, WA [UT] 

Rep. Edison Electric Institute 

(Alt. to K. E. Jannot) 
Charles W. Forsberg, OH [M] 

Rep. Society of the Plastics Industry Inc. 

(Alt. to D. H. Kendall) 
Jack A. Gruber, Wheatland Tube Co., PA [M] 

Rep. American Iron and Steel Institute 

(Alt. to R. E. Loyd) 
Alan Manche, Schneider Electric/Square D Company, KY [M 

Rep. National Electrical Manufacturers Association 

(Alt. to G. R. Dauberger) 



Von Dewayne Stelljes, Jr., Wayne's Electric, Inc., CO [IM] 

Rep. Independent Electrical Contractors 

(Alt. to C.E.Reynolds) 
Richard Temblador, Alflex Corporation, CA, [M] 

Rep. The Aluminum Association 

(Alt.toJ.C.Dollins) 
Ronald J. Toomer, Toomer Electrical Co. Inc., LA [IM] 

Rep. National Electrical Contractors Association 

(Alt. toS.P. Poholski) 
James Van Den Heuvel, West Electric Inc., WI [IM] 

Rep. Associated Builders and Contractors, Inc. 

(Alt. toJ.S.Corry) 
William C. Wagner, Underwriters Laboratories, Inc., NY [RT] 

(Alt. to R. Berman) 



CODE-MAKING PANEL NO. 9 

Articles 312, 314, 404, 408 

Timothy M. Croushore, Chair [UT] 

Allegheny Power Service Corp., PA 

Rep. Edison Electric Institute 



Boyd H. Culp, Phillips Petroleum Co., OK [U] 

Rep. American Chemistry Council 
Dale R. Deming, Am Electric Co. (T&B), MI [M] 
Frederic P. Hartwell, Hartwell Electrical Services, MA [SE] 
Jeffrey H. Hidaka, Underwriters Laboratories, IL [RT] 
Robert J. Kaemmerlen, Kaemmerlen Electric Co., MO [IM] 

Rep. National Electrical Contractors Association 
Thomas J. LeMay, LeMay Electric, Inc., GA [IM] 

Rep. Independent Electrical Contractors, Inc. 
Anthony Montuori, The New York Board of Fire Underwriters, 
NY [E] 

Rep. International Association of Electrical Inspectors 
Ronald H. Reed, Square D Company, KY [M] 

Rep. National Electrical Manufacturers Association 
Sukanta Sengupta, FMC Corp., NJ [U] 

Rep. Institute of Electrical & Electronics Engineers, Inc. 
Paul Welnak, IBEW Local 494, WI [L] 

Rep. International Brotherhood of Electrical Workers 



Alternates 



Mark R. Berner, PP&L, Inc., PA [UT] 

Rep. Edision Electric Institute 

(Alt. to T. M. Croushore) 
Jeff Bernson, IBEW, IL [L] 

Rep. International Brotherhood of Electrical Workers 

(Alt. to P. Welnak) 
Donald Offerdahl, ND State Electrical Board, ND [E] 

Rep. International Association of Electrical Inspectors 

(Alt. to A. Montuori) 
Bradford D. Rupp, Allied Moulded Products, Inc., OH [M] 

Rep. National Electrical Manufacturers Association 

Alt. to R. H. Reed 
Jerome W. Seigel, CT [U] 

Rep. Institute of Electrical & Electronics Engineers, Inc. 

(Alt. to S. Sengupta) 
Michael W. Wedel, Phillips Petroleum Company, TX [U] 

Rep. American Chemistry Council 

(Alt. to B.H. Culp) 



CODE-MAKING PANEL NO. 10 

Articles 240, 780 

James T. Dollard, Jr. Chair [L] 

IBEW, PA 

Rep. International Brotherhood of Electrical Workers 



Charles K. Blizard, American Electrical Testing Co., Inc., MA 
[IM] 

Rep. International Electrical Testing Association Inc. 
Madeline Borthick, IEC of Houston, TX [IM] 

Rep. Independent Electrical Contractors, Inc. 
John E. Brezan, Lehigh Valley Electrical Inspection Service, 
PA [E] 

Rep. International Association of Electrical Inspectors 
Robert J. Deaton, Union Carbide Corp., TX [U] 

Rep. Institute of Electrical & Electronics Engineers, Inc. 



Charles K. Eldridge, Indianapolis Power & Light Co., IN [UT] 

Rep. Edison Electric Institute 
Carl J. Fredericks, The Dow Chemical Co., TX [U] 

Rep. American Chemistry Council 
Don W. Jhonson, Interior Electric, Inc., FL [IM] 

Rep. National Electrical Contractors Association 
Clive W. Kimblin, Cutler-Hammer, Inc., PA [M] 

Rep. National Electrical Manufacturers Association 
Arden L. Munson, Hussmann Corp., MO [M] 

Rep. Air Conditioning and Refrigeration Institute 



2002 Edition 



NATIONAL ELECTRICAL CODE 



NATIONAL ELECTRICAL CODE COMMITTEE 



70-15 



• 



George J. Ockuly, MO [M] 

John A. Zaplatosch, Underwriters Laboratories Inc., IL [RT] 

Alternates 
David E. Chartrand, Middle Department Inspection Agency, 
Inc., NY [E] 

Rep. International Association of Electrical Inspectors 

(Alt. to J. E. Brezan) 
George D. Gregory, Square D Co., IA [M] 

Rep. National Electrical Manufacturers Association 

(Alt.toC.W.Kimblin) 
Roderic L. Hageman, Prit Service, Inc., IL [IM] 

Rep. International Electrical Testing Association Inc. 

(Alt.toC.K.Blizard) 
Charles D. Hughes, Westinghouse Savannah River Co., SC [U] 

Rep. Institute of Electrical & Electronics Engineers, Inc. 

(Alt. toR. J. Deaton) 
Randy Jones, IBEW Local 934, TN [L] 

Rep. International Brotherhood of Electrical Workers 

(Alt. toJ.T.Dollard,Jr.) 



Kris Mantravadi, La Roche Industries, LA [U] 

Rep. American Chemistry Council 

(Alt. to C.J. Fredericks) 
Paul J. Notarian, Underwriters Laboratories Inc., NY [RT] 

(Alt. to J. A. Zaplatosch) 
Vincent J. Saporita, Cooper Bussmann, MO [M] 

(Alt. to G. J. Ockuly) 
Steve A. Struble, Freeman's Electric Service, Inc., SD [IM] 

Rep. Independent Electrical Contractors 

(Alt. to M. Borthick) 
John Tolbert, Bristol Compressors, VA [M] 

Rep. Air Conditioning and Refrigeration Institute 

(Alt. to A. L. Munson) 
Leslie R. Zieike, South Carolina Electric and Gas Co., SC [UT] 

Rep. Edison Electric Institute 

(Alt.toC.K.Eldridge) 

Nonvoting 
Rick C. Gilmour, Canadian Standards Assn., ON 



CODE-MAKING PANEL NO. 11 

Articles 430, 440, 670, Appendix D Example D8 

Thomas H. Wood, Chair 
Cecil B Wood Inc., IL [IM] 
Rep. National Electrical Contractors Association 



• 



Rick L. Bunch, Tecumseh Products Co., MI [M] 

Rep. Air Conditioning and Refrigeration Institute 
Louis D. Closson, Intertek Testing Services, N.A. Inc., NY [RT] 
Joe David Cox, Eastman Chemical Co., TN [U] 

Rep. American Chemistry Council 
Thomas J. Garvey, State of Wisconsin, WI [E] 

Rep. International Association of Electrical Inspectors 
Paul S. Hamer, Chevron Research & Technology Co., CA [U] 

Rep. American Petroleum Institute 
Michael D. Landolfi, Landolfi Electric Co. Inc., NJ [IM] 

Rep. Associated Builders and Contractors, Inc. 
James M. Naughton, IBEW Local 103, MA [L] 

Rep. International Brotherhood of Electrical Workers 
Richard A. Rasmussen, Underwriters Laboratories, Inc., NC 
[RT] 

Vincent J. Saporita, Cooper Bussmann, MO [M] 
Lynn F. Saunders, GM Worldwide Facilities Group, MI [U] 

Rep. Institute of Electrical & Electronics Engineers, Inc. 
Charles B. Schram, Scottsdale, AZ [SE] 
M. Edward Thomas, Alabama Power Co., AL [UT] 

Rep. Edison Electric Institute 
Ron Widup, Shermco Industries, Inc., TX [IM] 

Rep. International Electrical Testing Association Inc. 
James R. Wright, Siemens-Furnas Controls, IL [M] 

Rep. National Electrical Manufacturers Association 

Alternates 

Frederick Bried, Equilon Enterprises LLC, TX [U] 

Rep. American Petroleum Institute 

(Alt. to PS. Hamer) 
Michael D'Amico, IBEW Local 488, CT [L] 

Rep. International Brotherhood of Electrical Workers 

(Alt. to J. M. Naughton) 



Elwood J. Dodge, Addison Products Co., FL [M] 

Rep. Air Conditioning and Refrigeration Institute 

(Alt. to R.L. Bunch) 
Stanley Folz, Folz Electric, Inc., IL [IM] 

Rep. National Electrical Contractors Association 

(Alt. to T.H.Wood) 
William D. Glover, PPG Industries, Inc., WV [U] 

Rep. American Chemistry Council 

(Alt. to J. D. Cox) 
Paul E. Guidry, Fluor Daniel, Inc., TX [IM] 

Rep. Associated Builders and Contractors, Inc. 

(Alt. to M.D. Landolfi) 
Leo H. Haas, Jr., Reliant Energy HLP, TX [UT] 

Rep. Edison Electric Institute 

(Alt. to M. E. Thomas) 
Robert J. Keough, U.S. Electrical Motors, MO [M] 

Rep. National Electrical Manufacturers Association 

(Alt. to J. R.Wright) 
George J. Ockuly, MO [M] 

(Alt. to V.J. Saporita) 
Carl Radcliffe, Underwriters Laboratories Inc., NC [RTJ 

(Alt. to R. A. Rasmussen) 
John A. Schultz, Minnesota Board of Electricity, MN [E] 

Rep. International Association of Electrical Inspectors 

(Alt. to T. J. Garvey) 
Arthur J. Smith, III, Waldemar S. Nelson and Co., Inc., LA [U] 

Rep. Institute of Electrical & Electronics Engineers, Inc. 

(Alt. to L. F. Saunders) 

Nonvoting 
Nino Mancini, 

Rep. Canadian Standards Association International, ON 



NATIONAL ELECTRICAL CODE 



2002 Edition 



70-16 



NATIONAL ELECTRICAL CODE COMMITTEE 



CODE-MAKING PANEL NO. 12 

Articles 426, 427, 610, 620, 625, 630, 645, 660, 665, 668, 669, 685, and Appendix D Examples D9 and D10 

Charles M. Trout, Chair [IM] 

Maron Electric Co., FL 

Rep. National Electrical Contractors Association 



Thomas M. Burke, Underwriters Laboratories Inc., CA [RT] 
Andre R. Cartal, Borough of Princeton, NJ [E] 

Rep. International Association of Electrical Inspectors 
James E Cook, Eagle Electric Manufacturing, NY [M] 

Rep. National Electrical Manufacturers Association 
Kent B. Givens, Aluminum Co. of America, TX [M] 

Rep. The Aluminum Association 

(VL 427, 610, 625, 630, 645, 646, 660, 665, 668, 669 and 685) 
Bill Hanthorn, BICC General Pyrotenax Cables Ltd., ON [M] 

Rep. Copper Development Association Inc. 
Robert A. Jones, Independent Electrical Contractors, TX [IM] 

Rep. Independent Electrical Contractors, Inc. 
William J. Kelly, Eastman Kodak Co., NY [U] 

Rep. Institute of Electrical & Electronics Engineers, Inc. 
Richard H. Laney, Siecor Corp., NC [U] 
Nick Marchitto, Otis Elevator Co., CT [M] 

Rep. National Elevator, Inc. 

(VL 610, 620 and 630) 
John H. Mortimer, Inductotherm Corp., NJ [M] 

(VL 665) 
NorbertPoch, IBM Corp., MN [U] 

Rep. Information Technology Industry Council 

(VL 645) 
Ronald L. Purvis, Georgia Power Co., GA [UT] 

Rep. Edison Electric Institute 
David R. Quave, Int'l. Brotherhood of Electrical Workers, MS [L] 

Rep. International Brotherhood of Electrical Workers 
Robert H. Reuss, Morris Material Handling, LLC, WI [M] 

(VL 610) 
T. Neil Thorla, Inland Steel Co., IN [U] 

Rep. Association of Iron & Steel Engineers 

(VL 610, 620, and 630) 
Craig B. Toepfer, Ford Motor Co., MI [U] 

Rep. Society of Automotive Engineers 

(VL 625) 
Kenneth P. White, Olin Corp., NY [U] 

Rep. American Chemistry Council 

Alternates 
Scott Cline, McMurtrey Electric, Inc., CA [IM] 
Rep. National Electrical Contractors Association 
(Alt. to C. M. Trout) 



Kenneth Hartwig, Daimler Chrysler, MI [U] 

Rep. Society of Automotive Engineers 

(Alt. to C.B. Toepfer) 

(VL 625) 
Jeffrey H. Hidaka, Underwriters Laboratories, IL [RT] 

(Alt. to T.M.Burke) 
Robert E. Johnson, Motorola, MA [U] 

Rep. Information Technology Industry Council 

(Alt. to N. Poch) 

(VL 645) 
Andy Juhasz, Kone Inc., IL [M] 

Rep. National Elevator Industry Inc. 

(Alt. to N. Marchitto) 

(VL 610, 620 and 630) 
Roger D. McDaniel, Georgia Power Co., GA [UT] 

Rep. Edision Electric Institute 

(Alt. to R. L. Purvis) 
Harold C. Ohde, Int'l. Brotherhood of Electrical Workers, IL [L] 

Rep. International Brotherhood of Electrical Workers 

(Alt. to D. R. Quave) 
Robert C. Oldham, Jr., Reynolds Metals Co., VA [M] 

Rep. The Aluminum Association 

(Alt. to K.B. Givens) 

(VL 427, 610, 625, 630, 645, 646, 660, 665, 668, 669, and 685) 
Merritt D. Redick, M. Redick & Associates, CA [U] 

Rep. Institute of Electrical & Electronics Engineers, Inc. 

(Alt. to W. J. Kelly) 
James J. Rogers, Massachusetts St. Board of Electrical 
Examiners, MA [E] 

Rep. International Association of Electrical Inspectors 

(Alt. to A. R. Cartal) 
George S. Tidden, IEC, TX [IM] 

Rep. Independent Electrical Contractors, Inc. 

(Alt. to R.A.Jones) 
Robert C. Turner, Inductotherm Corp., NJ [M] 

(Alt. to J. H. Mortimer) 

(VL 665) 
James E. Winfrey, Square D Co., NC [M] 

Rep. National Electrical Manufactuers Association 

(Alt. to J. F. Cook) 



CODE-MAKING PANEL NO. 13 

Articles 450, 455, 460, 470, 490 

William T. O'Grady, Chair [RT] 
Underwriters Laboratories Inc., NY 



Tarry L. Baker, Broward County Board of Rules and Appeals, 
FL [E] 

Rep. International Association of Electrical Inspectors 
William A. Brunner, IBEW, ND [L] 

Rep. International Brotherhood of Electrical Workers 
James C. Carroll, Square D Co., TN [M] 

Rep. National Electrical Manufacturers Association 
William B. Crist, Houston Stafford Electric Company, TX [IM] 

Rep. Independent Electrical Contractors, Inc. 



O. L. Davis, Manzano Western, Inc., NM [IM] 

Rep. National Electrical Contractors Association 
Richard P. Fogarty, Jr., Consolidated Edison Co. of N.Y., Inc. 
NY [UT] 

Rep. Edison Electric Institute 
Milton D. Robinson, Milt Robinson Engineering Co., IN [U] 

Rep. Institute of Electrical & Electronics Engineers, Inc. 
LaVerne E. Stetson, U.S. Dept. of Agriculture, NE [U] 

Rep. American Society of Agricultural Engineers 



2002 Edition 



NATIONAL ELECTRICAL CODE 



NATIONAL ELECTRICAL CODE COMMITTEE 



70-17 



• 



Lou G. Willoughby, ALCOA Inc., OH [M] 

Rep. The Aluminum Association 
Ralph H. Young, Eastman Chemical Co., TN [U] 

Rep. American Chemistry Council 

Alternates 

Douglas Elkins, Exxon Chemical Co., TX [U] 

Rep. American Chemistry Council 

(Alt. to R.H.Young) 
Timothy D. HoIIeman, AC Corp., NC [IM] 

Rep. Independent Electrical Contractors, Inc. 

(Alt. to W.B.Crist) 
Barry N. Hornberger, PECO Energy Co., PA [UT] 

Rep. Edison Electric Institute 

(Alt.toR.P.Fogarty,Jr.) 
Richard Lofton, IBEW Local 280, OR [L] 

Rep. International Brotherhood of Electrical Workers 

(Alt. toW.A.Brunner) 
Arthur Mastromarino, Underwriters Laboratories Inc., NY 
[RT] 

(Alt. to W. T. O'Grady) 



Gene Morehart, Acme Electric Corp., NC [M] 

Rep. National Electrical Manufacturers Association 

(Alt. to J. C. Carroll) 
Robert L. Simpson, Simpson Electrical Engineering Co., GA 
[U] 

Rep. Institute of Electrical & Electronics Engineers, Inc. 

(Alt. to M. D. Robinson) 
Monte Szendre, Wilson construction Co., OR [IM] 

Rep. National Electrical Contractors Association 

(Alt. to O. L. Davis) 
Gerald W.Williams, County of Ventura, CA [E] 

Rep. International Association of Electrical Inspectors 

(Alt. to T. L. Baker) 
Ivan L. Winsett, Ronk Electrical Industries, GA [U] 

Rep. American Society of Agricultural Engineers 

(Alt. to L. E. Stetson) 



CODE-MAKING PANEL NO. 14 

Articles 500, 501, 502, 503, 504, 505, 510, 511, 513, 514, 515 and 516 

Donald R. Cook, Chair 

Shelby County Bldg. Inspections, AL [E] 

Rep. International Association of Electrical Inspectors 



Robert B. Alexander, Fluor Daniel, Inc., CA [IM] 

Rep. Associated Builders and Contractors, Inc. 
Edward M. Briesch, Underwriters Laboratories Inc., IL [RT] 
Al Engler, EGS Electrical Group, IL [M] 

Rep. International Society for Measurement and Control 
Mark Goodman, BP(ARCO),CA [U] 

Rep. American Petroleum Institute 
Doug Jagunich, Intertek Testing Services, N.A., Inc., MN [RT] 
Joseph H. Kuczka, Killark Electric Mfg. Co., MO [M] 

Rep. National Electrical Manufacturers Association 
William G. Lawrence, Jr., FM Global, MA [I] 
Mike O'Meara, Arizona Public Service Co., AZ [UT] 

Rep. Edison Electric Institute 
Mark G. Saban, Saban Electric, IL [IM] 

Rep. National Electrical Contractors Association 
David Wechsler, Union Carbide Corp., WV [U] 

Rep. American Chemistry Council 
James A. Weldon, IBEW Local 728, FL [L] 

Rep. International Brotherhood of Electrical Workers 
Donald W. Zipse, Zipse Electrical Engineering Inc., PA [U] 

Rep. Institute of Electrical & Electronics Engineers, Inc. 

Alternates 
Alonza W. Ballard, Crouse-Hinds, NY [M] 

Rep. National Electrical Manufacturers Association 

(Alt. to J. H. Kuczka) 
James D. Cospolich, Waldemar S.Nelson & Co. Inc., LA [U] 

Rep. Institute of Electrical & Electronics Engineers, Inc. 

(Alt. to D.W. Zipse) 
William T. Fiske, Intertek Testing Services N.A. Inc., NY [RT] 

(Alt. to D. Jagunich) 
Larry E. Fuhrman, City of Titusville, FL [E] 

Rep. International Association of Electrical Inspectors 

(Alt. to D.R.Cook) 



Paul T. Kelly, Underwriters Laboratories Inc., IL [RT] 

(Alt. to E. M. Briesch) 
Harold C. Kronz, IBEW Local 308, FL [L] 

Rep. International Brotherhood of Electrical Workers 

(Alt. to J. A. Weldon) 
Michael E. McNeil, FMC Corp/Bio Polymer, ME [U] 

Rep. American Chemistry Council 

(Alt. to D. Wechsler) 
Thomas F. Mueller, Southern Company Generation, AL [UT] 

Rep. Edison Electric Institute 

(Alt. to M. O'Meara) 
Peter T. Schimmoeller, FM Global, MA [I] 

(Alt. to W. G. Lawrence, Jr.) 
Ted H. Schnaare, Rosemount Inc., MN [M] 

Rep. International Society for Measurement and Control 

(Alt. to A. Engler) 
Francis M. Stone, Jr., Shell Exploration and Production Co., TX, 
[U] 

Rep. American Petroleum Institute 

(Alt. to M. Goodman) 
Mark C. Wirfs, R & W Engineering Inc., OR [U] 

Rep. Grain Elevator & Processing Society 

(Voting Alt. to GEAPS Rep.) 

Nonvoting 

Eduardo N. Solano, Estudio Ingeniero Solano S. A., Argentia 
[SE] 

Fred K.Walker, U.S. Air Force, FL [U] 
Rep. TC on Airport Facilities 



NATIONAL ELECTRICAL CODE 



2002 Edition 



70-18 



NATIONAL ELECTRICAL CODE COMMITTEE 



CODE-MAKING PANEL 15 

Articles 445, 480, 518, 520, 525, 530, 540, 647, 695, 700, 701, 702, 705 

Robert C. Duncan, Chair [E] 

Reedy Creek Improvement District, FL 

Rep. International Association of Electrical Inspectors 



Peter W. Amos, Consolidated Edison Co. of N.Y., Inc., NY [UT] 

Rep. Edison Electric Institute 
James L. Boyer, Firetrol, Inc., NC [M] 

Rep. National Electrical Manufacturers Association 
Brian Burrows, IBEW Local 98, PA [L] 

Rep. International Brotherhood of Electrical Workers 
Tom Dunn, Butler Amusements, CA [U] 

Rep. Outdoor Amusement Business Association, Inc. 

(VL 525) 
George W. Flach, Flach Consultants, LA [SE] 
Michael V. Glenn, Longview Fibre Co., WA [U] 

Rep. Institute of Electrical & Electronics Engineers, Inc. 
Marcelo M. Hirschler, GBH Int'L, CA [SE] 
George Thomas Howard, George Thomas Howard & 
Associates, NV [SE] 
Gordon S. Johnson, Dundee, FL [M] 

Rep. Electrical Generating Systems Association 
Robert J. Kakalec, Telcordia Technologies, NJ [UT] 

Rep. Alliance for Telecommunications Industry Solutions 

(VL 445, 480, 700, 701, 702, and 705) 
Jack W. Kalbfeld, Kalico Technology Inc., NY [SE] 

(VL 518, 520, 525, 530, and 540) 
Michael B. Klein, Consentini Associates DC, LLP, MD [IM] 

Rep. Illuminating Engineering Society of North America 
John R. Kovacik, Underwriters Laboratories Inc., IL [RT] 
Edwin S. Kramer, Radio City Music Hall, NY [L] 

Rep. Int'l. Association of Theatrical Stage Employees 
Michael A. Lanni, Universal Studios, CA [U] 

Rep. Motion Picture Association of America, Inc. 
Dennis W. Marshall, TAG Electric Co., TX [IM] 

Rep. Independent Electrical Contractors 
Steven H. Pasternack, Intertek Testing Services, N. A. Inc., NY 
[RT] 
Richard Sobel, Quantum Electric Corp., NY [IM] 

Rep. National Electrical Contractors Association 



Dale A. Triffo, Equilon Enterprises LLC, TX [U] 

Rep. American Chemistry Council 
Kenneth E. Vannice, NSI Corp., OR [M] 

Rep. US Institute for Theatre Technology 

Alternates 
Mike Grunwald, IBEW Local 76, WA [L] 

Rep. International Brotherhood of Electrical Workers 
(Alt. to B. Burrows) 

Mitchell K. Hefter, Rosco Entertainment Technology, OR [IM] 
Rep. Illuminating Engineering Society of North America 
(Alt. to M.B.Klein) 

Natalie J. McCord, AEP, Public Service Co. of Oklahoma, OK 
[UT] 

Rep. Edison Electric Institute 

(Alt. to P. W. Amos) 

Rep. National Electrical Manufacturers Association 

(Alt. to J. L. Boyer) 
Michael D. Skinner, CBS Studio Center, CA [U] 

Rep. Motion Picture Association of America, Inc. 

(Alt. to M. A. Lanni) 
Steven R. Terry, Production Resource Group LLC, Fourth Phase, 
NJ [U] 

Rep. US Institute for Theatre Technology 

(Alt. to K.E. Vannice) 
Herbert V. Whittall, Electrical Generating Systems Assn., FL 
[M] 

Rep. Electrical Generating Systems Association 

(Alt. to G.S.Johnson) 
Harold F. Willman, City of Lakewood, CO [E] 

Rep. International Association of Electrical Inspectors 

(Alt. to R. C. Duncan) 



CODE-MAKING PANEL NO. 16 

Articles 640, 650, 720, 725, 727, 760, 770, 800, 810, 820, 830, and Chapter 9 Tables 11(a) and (b) and 12(a) and (b) 

Stanley D. Kahn, Chair [IM] 

Tri-City Electric Co., Inc., CA 

Rep. National Electrical Contractors Association 



James E. Brunssen, Telcordia Technologies, Inc., NJ [UT] 

Rep. Alliance for Telecommunications Industry Solutions 
Orren E. Cameron, III, United States Dept. of Agriculture, DC 
[UT] 
Loren M. Caudill, The DuPont Company, DE [M] 

Rep. Society of the Plastics Industry Inc. 
Gerald Lee Dorna, Belden Wire & Cable, IN [M] 

Rep. Insulated Cable Engineers Association Inc. 
Roland W. Gubisch, Intertek Testing Services, N.A. Inc., MA 
[RT] 

Lee C. Hewitt, Underwriters Laboratories Inc., IL [RT] 
William K. Hopple, Simplex Time Recorder Co., CA [M] 

Rep. National Electrical Manufacturers Association 



Robert L. Hughes, DuPont, TN [U] 

Rep. American Chemistry Council 
Steven C. Johnson, Time Warner Cable, CO [UT] 

Rep. National Cable Television Association 
Ronald G. Jones, Ronald G. Jones, TX [U] 

Rep. Institute of Electrical & Electronics Engineers, Inc. 
Stanley Kaufman, Lucent Technologies, GA [M] 
Michael A. Lanni, Universal Studios, CA [U] 

Rep. Motion Picture Association of America, Inc. 
John Mangan, Medford City Hall, MA [E] 

Rep. International Association of Electrical Inspectors 
J. Jeffrey Moore, Industrial Risk Insurers, OH [I] 

Rep. Industrial Risk Insurers 



2002 Edition 



NATIONAL ELECTRICAL CODE 



NATIONAL ELECTRICAL CODE COMMITTEE 



70-19 



James W. Romlein, MIS Labs, WI [M] 

Rep. Building Industry Consulting Service International 
Arthur E. Schlueter, Jr., A. E. Schlueter Pipe Organ Co., GA [M] 

(VL 640, 650, 720, and 725) 
Steven M. Speer, IBEW Local 640, AZ [L] 

Rep. International Brotherhood of Electrical Workers 
Kyle E.Todd, Entergy -GSU,TX [UT] 

Rep. Edison Electric Institute 
Inder L. Wadehra, IBM Corp., NC [U] 
Melvin J. Wierenga, Wierenga & Associates, MI [IM] 

Alternates 
Ronald P. Cantrell, IBEW Local 72, TX [L] 

Rep. International Brotherhood of Electrical Workers 

(Alt. to S.M. Speer) 
Larry Chan, City of New Orleans, LA [E] 

Rep. International Association of Electrical Inspectors 

(Alt. to J. Mangan) 
Chrysanthos Chrysanthou, Telcordia Technologies, Inc., NI 
[UT] 

Rep. Alliance for Telecommunications Industry Solutions 

(Alt. to J. E. Brunssen) 
A. William Coaker, A. W. Coaker and Associates, Inc., OH [M] 

Rep. Society of the Plastics Industry Inc. 

(Alt. to L. M. Caudill) 
Gilbert J. Diaz, Intertek Testing Services, N.A. Inc., TX [RT] 

(Alt. to R. W. Gubisch) 
Richard S. Houghten, MI [M] 

(Alt. to A. E. Schlueter, Ir.) 

(VL 640, 650, 720, and 725) 



Robert Jensen, dbi - Telecommunication Infrastructure Design, 
TX [M] 

Rep. Building Industry Consulting Service International 

(Alt. to J. W. Romlein) 
William J. McCoy, Verizon Wireless, TX [U] 

Rep. Institute of Electrical & Electronics Engineers, Inc. 

(Alt. to R. G. Jones) 
W. D. Pirkle, Pirkle Electric Co., Inc., GA [IM] 

Rep. National Electrical Contractors Association 

(Alt.toS.D.Kahn) 
Bradley C. Rowe, Underwriters Laboratories Inc., IL [RT] 

(Alt. to L. C. Hewitt) 
Oleh Sniezko, AT&T Broadband, CO [UT] 

Rep. National Cable Television Association 

(Alt. to S.C.Johnson) 
Sondra K. Todd, Western Resources Co., KS [UT] 

Rep. Edison Electric Institute 

(Alt. to K. E. Todd) 
Lawrence J. Wenzel, Industrial Risk Insurers, CT [I] 

(Alt. to J. J. Moore) 
Kevin D. Wilhelm, Eli Lilly and Co., IN [U] 

Rep. American Chemistry Council 

(Alt. to R. L. Hughes) 
Joe Rao, RAO Electric Co., FL [IM] 

Rep. Independent Electrical Contractors, Inc. 

(Voting Alt. to IEC Rep.) 

Nonvoting 
Irving Mande, Edwards Systems Technology, CT 



CODE-MAKING PANEL NO. 17 

Article 517 

Robert E. Bernd, Chair [RT] 
Underwriters Laboratories Inc., IL 



Steve Campolo, Leviton Manufacturing Co., Inc., NY [M] 

Rep. National Electrical Manufacturers Association 
Thomas C. Clark, Clark Electrical Construction, Inc., TX [IM] 

Rep. Associated Builders and Contractors, Inc. 
James R. Duncan, Sparling, WA [U] 

Rep. Institute of Electrical & Electronics Engineers, Inc. 
Douglas S. Erickson, American Society for Healthcare Engineer- 
ing, VI [U] 

Rep. American Society for Healthcare Engineering 
James W. Hillebrand, Byron Electric Co., KY [IM] 

Rep. National Electrical Contractors Association 
James A. Meyer, Pettis Memorial VA Hospital, CA [C] 

Rep. American Society of Anesthesiologists 
Hugh O. Nash, Jr., Nash Lipsey Burch, LLC, TN [SE] 
Donald J. Sheratt, Intertek Testing Services, N.A. Inc., MA 
[RT] 
Richard H. Smith, OG&E Electric Services, OK [UT] 

Rep. Edison Electric Institute 
Jeffrey L. Steplowski, U.S. Dept. of Veterans Affairs, DC [U] 
Mike Velvikis, High Voltage Maintenance Corp., WI [IM] 

Rep. International Electrical Testing Association Inc. 
Walter N. Vernon, IV, Mazzetti & Associates Inc., CA [U] 

Rep. NFPA Health Care Section 
Andrew White, WFJEATC Local Union 3 IBEW, NY [L] 

Rep. International Brotherhood of Electrical Workers 



Alternates 



Matthew B. Dozier, Smith Seckman Reid, Inc., TN [U] 

Rep. Institute of Electrical & Electronics Engineers, Inc. 

(Alt. to J. R.Duncan) 
Banks Hattaway, Hattaway Brothers Inc., AL [IM] 

Rep. Associated Builders and Contractors, Inc. 

(Alt. to T.C.Clark) 
Stephen D. Hewson, Underwriters Laboratories Inc., IL [RT] 

(Alt. to R. E. Bernd) 
Stanley D. Kahn, Tri-City Electric Co., Inc., CA [IM] 

Rep. National Electrical Contractors Association 

(Alt. to J. W. Hillebrand) 
Paul L. LeVasseur, Bay City JEATC, MI [L] 

Rep. International Brotherhood of Electrical Workers 

(Alt. to A. White) 
David K. Norton, U.S. Dept. of Veterans Affairs, DC [U] 

(Alt. to J. L. Steplowski) 
Gaylen D. Rogers, DFCM, UT [E] 

Rep. International Association of Electrical Inspectors 

(Voting Alt. to IAEI Rep.) 



NATIONAL ELECTRICAL CODE 



2002 Edition 



70-20 



NATIONAL ELECTRICAL CODE COMMITTEE 



CODE-MAKING PANEL NO. 18 

Articles 406, 410, 411, 600, 605 

Wayne Brinkmeyer, Chair [IM] 

Biddle Electric Corp.,TX 

Rep. National Electrical Contractors Association 



Michael N.Ber,IEC, Houston, TX [IM] 

Rep. Independent Electrical Contractors, Inc. 
Robert L. Cochran, City of Costa Mesa, CA [E] 

Rep. International Association of Electrical Inspectors 
Rudy T. Elam, Systems Engineering Services, TN [U] 

Rep. Institute of Electrical & Electronics Engineers, Inc. 
Kenneth E Kempel, Underwriters Laboratories Inc., NC [RT] 
Thomas J. Lynch, IBEW Local 99, RI [L] 

Rep. International Brotherhood of Electrical Workers 
Bernard J. Mezger, American Lighting Assn., NY [M] 

Rep. American Lighting Association 

(VL 410 and 411) 
James E Pierce, Intertek Testing Services NA Inc., OR [RT] 
Saul Rosenbaum, Leviton Mfg. Co. Inc., NY [M] 

Rep. National Electrical Manufacturers Association 
Carl T. Wall, Alabama Power Co., AL [UT] 

Rep. Edison Electric Institute 
Jack Wells, Pass & Seymour/Legrand, NY [M] 

Alternates 

MarkR.Berner,PP&L,Inc.,PA [UT] 

Rep. Edison Electric Institute 

(Alt. to C. T. Wall) 
Robert T. Carlock, R. T. Carlock Co., TN [IM] 

Rep. Independent Electrical Contractors 

(Alt. to M. N. Ber) 



Howard D. Hughes, Hughes Electric Co. Inc., AR [IM] 

Rep. National Electrical Contractors Association 

(Alt. to W. Brinkmeyer) 
Stephen G. Kieffer, Kieffer & Co., Inc., WI [M] 

Rep. International Sign Association 

(Voting Alt. to ISA Rep.) 

(VL 600) 
Steven A. Larson, B WXT Y- 12 , TN [U] 

Rep. Institute of Electrical & Electronics Engineers, Inc. 

(Alt. to R.T. Elam) 
John J. Mahal, Underwriters Laboratories Inc., IL [RT] 

(Alt. to K.F. Kempel) 
Don Miletich, Cooper Lighting, IL [M] 

Rep. National Electrical Manufacturers Association 

(Alt. to S. Rosenbaum) 
Michael S. O'Boyle, Lightolier, Div. of Genlyte Thomas Group, 
MA [M] 

Rep. American Lighting Association 

(Alt. to B.J. Mezger) 

(VL 410 and 411) 
Charles M. Trout, Maron Electric Co., FL [IM] 

Rep. National Electrical Contractors Association 

(Alt. to W. Brinkmeyer) 



CODE-MAKING PANEL NO. 19 

Articles 545, 547, 550, 551, 552, 553, 555, 604, 675 

Robert A. McCullough, Chair [E] 

Ocean County Construction Inspection Dept., NJ 

Rep. International Association of Electrical Inspectors 



Barry Bauman, Alliant Energy, WI [U] 

Rep. American Society of Agricultural Engineers 
James W. Finch, Kampgrounds of America, Inc., MT [U] 

(VL 550, 551, 552, and 555) 
Bruce A. Hopkins, Recreation Vehicle Industry Assn., VA [M] 

Rep. Recreation Vehicle Industry Association 

(VL 550, 551, and 552) 
Steven Johnson, IBEW, CA [L] 

Rep. International Brotherhood of Electrical Workers 
Robert L. LaRocca, Underwriters Laboratories Inc., NY [RT] 
Timothy P. McNeive, Thomas & Betts Corp., TN [M] 

Rep. National Electrical Manufacturers Association 
Leslie Sabin, San Diego Gas & Electric Co., CA, UT 

Rep. Edison Electric Institute 
Charles F. Shy, AC Corp ./Electrical Division, NC [IM] 

Rep. Independent Electrical Contractors 
Dick Veenstra, Fleetwood Enterprises , Inc . , C A [M] 

Rep. Manufactured Housing Institute 

(VL 550, 551, and 552) 
Kenneth Weakley, Mountain Electric , Inc . , C A , [IM] 

Rep. National Electrical Contractors Association 
Michael L. Zieman, RADCO, CA [RT] 

(VL 545, 550, 551, and 552) 



Alternates 



Glenn H. Ankenbrand, Conectiv Power, MD [UT] 

Rep. Edison Electric Institute 

(Alt. to L. Sabin) 
Steven Blais, EGS - Electrical Group, IL [M] 

Rep. National Electrical Manufacturers Association 

(Alt. to T. P. McNieve) 
James K. Hinrichs, St. of Washington, WA [E] 

Rep. International Association of Electrical Inspectors 

(Alt. to R. A. McCullough) 
John Mikel, Skyline Corporation, IN [M] 

Rep. Manufactured Housing Institute 

(Alt. to D. Veenstra) 

(VL 550, 551, and 552) 
John Pabian, Underwriters Laboratories Inc., IL [RT] 

(Alt. to R. L. Larocca) 
Kent Perkins, Recreation Vehicle Industry Assn., VA [M] 

Rep. Recreation Vehicle Industry Association 

(Alt. to B.A.Hopkins) 

(VL 550, 551, and 552) 
Homer Staves, Kampgrounds of America, Inc., MT [U] 

(Alt. to J. W. Finch) 

(VL 550, 551, 552, and 555) 



2002 Edition 



NATIONAL ELECTRICAL CODE 



NATIONAL ELECTRICAL CODE COMMITTEE 



70-21 



La Verne E. Stetson, U.S. Dept. of Agriculture, NE [U] 

Rep. American Society of Agricultural Engineers 

(Alt. toB.Bauman) 
David N. Tilmont, IBEW Local 952, CA [L] 

Rep. International Brotherhood of Electrical Workers 

(Alt. to S.Johnson) 
Raymond F. Tucker, RADCO,C A [RT] 



(Alt. to M. L. Zieman) 
(VL 545, 550, 551 and 552) 
David Gorin, Nat'l. Assn. of RV Parks & Campgrounds, VA [U] 
Rep. Nat'l. Assn. of RV Parks & Campgrounds 
(Voting Alt. to ARVC rep.) 
(VL 550, 551, and 552) 



CODE-MAKING PANEL NO. 20 

Articles 422, 424, 680 

Robert M. Milatovich, Chair [E] 

Clark County, NV 

Rep. International Association of Electrical Inspectors 



Scott Cline, McMurtrey Electric, Inc., CA [M] 

Rep. National Electrical Contractors Association 
Robert J. Egan, Int'l. Brotherhood of Electrical Workers, MO [L] 

Rep. International Brotherhood of Electrical Workers 
Christopher Gill, New York Board of Fire Underwriters, NY [E] 
Walter Koessel, Intertek Testing Services, N.A. Inc., MO [RT] 
Neil F. LaBrake, Jr., Niagara Mohawk Power Corp., NY [UT] 

Rep. Edison Electric Institute 
James N. Pearse, Leviton Mfrg. Co. Inc., NY [M] 

Rep. National Electrical Manufacturers Association 
Marcos Ramirez, Mr. Electric Service Co., Inc., NY [IM] 

Rep. Independent Electrical Contractors, Inc. 
Anthony Sardina, Carrier Corp., NY [M] 

Rep. Air Conditioning and Refrigeration Institute 

(VL 422, 424, and 426) 
Donald J. Talka, UL Intrnational Germany GmbH [RT] 
John T. Weizeorick, WI [M] 

Rep. Association of Home Appliance Manufacturers 

(VL 422, 424, and 426) 
Lee L. West, Balboa Instruments, CA [M] 

Rep. National Spa and Pool Institute 

(VL 680) 
Robert M. Yurkanin, Electran Process Int'l. Inc., NJ [U] 

Rep. Institute of Electrical & Electronics Engineers, Inc. 

Alternates 

Xen George Anchales, San Bernardino County /Dept. of Bldg. & 
Safety, CA [E] 



Rep. International Association of Electrical Inspectors 

(Alt. to R. M. Milatovich) 
Dennis L. Baker, Springs & Sons Electrical Cont. Inc., AZ [IM] 

Rep. Independent Electrical Contractors 

(Alt. to M. Ramirez) 
Bruce R. Hirsch, Baltimore Gas & Electric Co., MD [UT] 

Rep. Edison Electric Institute 

(Alt. to N.F. LaBrake, Jr.) 
Mark Leimbeck, Underwriters Laboratories, Inc., IL [RT] 

(Alt. to D. J. Talka) 
Tom McDonald, Hubbell, Inc., CT [M] 

Rep. National Electrical Manufacturers Association 

(Alt. to J. N. Pearse) 
Stephen P. Schoemehl, Int'l. Brotherhood of Electrical Workers, 
MO [L] 

Rep. International Brotherhood of Electrical Workers 

(Alt. to R. J. Egan) 
Robert E. Wisenburg, Coates Heater Co., Inc., WA [M] 

Rep. National Spa and Pool Institute 

(Alt. to L. L. West) 

(VL 680) 

Nonvoting 
Rick C. Gilmour, Canadian Standards Assn., ON 
William H. King, Jr., U.S. Consumer Product Safety 
Commission, MD 

Andrew M. Trotta, U.S. Consumer Product Safety Commission, 
MD 

(Alt. to W. H. King, Jr.) 



NFPA Electrical Engineering Division Technical Staff 



Mark W. Earley, Assistant Vice President/Chief Electrical Engineer 

John M. Caloggero, Principal Electrical Specialist 

Kenneth G. Mastrullo, Senior Electrical Specialist 

Jean A. O'Connor, Electrical Project Specialist/Support Supervisor 



Lee F. Richardson, Senior Electrical Engineer 
Jeffrey S. Sargent, Senior Electrical Specialist 
Joseph V. Sheehan, Principal Electrical Engineer 



NFPA Staff Editor 
Joyce G. Grandy, Senior Project Editor 

NOTE: Membership on a committee shall not in and of itself constitute an endorsement of the Association 
or any document developed by the committee on which the member serves. 

Committee Scope: This Committee shall have primary responsibility for documents on minimizing the 
risk of electricity as a source of electric shock and as a potential ignition source of fires and explosions. 
It shall also be responsible for text to minimize the propagation of fire and explosions due to electrical 
installations. 



NATIONAL ELECTRICAL CODE 



2002 Edition 



ARTICLE 80 — ADMINISTRATION AND ENFORCEMENT 



70-23 



NFPA 70 
National Electrical Code® 

2002 Edition 

ARTICLE 80 
Administration and Enforcement 



This article is informative unless specifically adopted 
by the local jurisdiction adopting the National Electrical 
Code®. (See 80.5.) 

80.1 Scope. The following functions are covered: 

(1) The inspection of electrical installations as covered by 
90.2 

(2) The investigation of fires caused by electrical installa- 
tions 

(3) The review of construction plans, drawings, and speci- 
fications for electrical systems 

(4) The design, alteration, modification, construction, 
maintenance, and testing of electrical systems and 
equipment 

(5) The regulation and control of electrical installations at 
special events including but not limited to exhibits, 
trade shows, amusement parks, and other similar spe- 
cial occupancies 

80.2 Definitions. 

Authority Having Jurisdiction. The organization, office, 
or individual responsible for approving equipment, materi- 
als, an installation, or a procedure. 

Chief Electrical Inspector. An electrical inspector who 
either is the authority having jurisdiction or is designated 
by the authority having jurisdiction and is responsible for 
administering the requirements of this Code. 

Electrical Inspector. An individual meeting the require- 
ments of 80.27 and authorized to perform electrical inspec- 
tions. 

80.3 Purpose. The purpose of this article shall be to pro- 
vide requirements for administration and enforcement of 
the National Electrical Code. 

80.5 Adoption. Article 80 shall not apply unless specifi- 
cally adopted by the local jurisdiction adopting the Na- 
tional Electrical Code. 

80.7 Title. The title of this Code shall be NFPA 70, Na- 
tional Electrical Code®, of the National Fire Protection 
Association. The short title of this Code shall be the NEC®. 



80.9 Application. 

(A) New Installations. This Code applies to new installa- 
tions. Buildings with construction permits dated after adop- 
tion of this Code shall comply with its requirements. 

(B) Existing Installations. Existing electrical installations 
that do not comply with the provisions of this Code shall be 
permitted to be continued in use unless the authority having 
jurisdiction determines that the lack of conformity with this 
Code presents an imminent danger to occupants. Where 
changes are required for correction of hazards, a reasonable 
amount of time shall be given for compliance, depending 
on the degree of the hazard. 

(C) Additions, Alterations, or Repairs. Additions, alter- 
ations, or repairs to any building, structure, or premises 
shall conform to that required of a new building without 
requiring the existing building to comply with all the re- 
quirements of this Code. Additions, alterations, installa- 
tions, or repairs shall not cause an existing building to be- 
come unsafe or to adversely affect the performance of the 
building as determined by the authority having jurisdiction. 
Electrical wiring added to an existing service, feeder, or 
branch circuit shall not result in an installation that violates 
the provisions of the Code in force at the time the additions 
are made. 

80.11 Occupancy of Building or Structure. 

(A) New Construction. No newly constructed building 
shall be occupied in whole or in part in violation of the 
provisions of this Code. 

(B) Existing Buildings. Existing buildings that are occu- 
pied at the time of adoption of this Code shall be permitted 
to remain in use provided the following conditions apply: 

(1) The occupancy classification remains unchanged 

(2) There exists no condition deemed hazardous to life or 
property that would constitute an imminent danger 

80.13 Authority. Where used in this article, the term au- 
thority having jurisdiction shall include the chief electrical 
inspector or other individuals designated by the governing 
body. This Code shall be administered and enforced by the 
authority having jurisdiction designated by the governing 
authority as follows. 



(1) The authority having jurisdiction shall be permitted to 
render interpretations of this Code in order to provide 
clarification to its requirements, as permitted by 90.4. 

(2) When the use of any electrical equipment or its instal- 
lations is found to be dangerous to human life or prop- 
erty, the authority having jurisdiction shall be empow- 
ered to have the premises disconnected from its 
source of electric supply, as established by the Board. 



NATIONAL ELECTRICAL CODE 



2002 Edition 



70-24 



ARTICLE 80 — ADMINISTRATION AND ENFORCEMENT 



When such equipment or installation has been so con- 
demned or disconnected, a notice shall be placed 
thereon listing the causes for the condemnation, the 
disconnection, or both and the penalty under 80.23 for 
the unlawful use thereof. Written notice of such con- 
demnation or disconnection and the causes therefor 
shall be given within 24 hours to the owners, the oc- 
cupant, or both, of such building, structure, or pre- 
mises. It shall be unlawful for any person to remove 
said notice, to reconnect the electric equipment to its 
source of electric supply, or to use or permit to be 
used electric power in any such electric equipment 
until such causes for the condemnation or disconnec- 
tion have been remedied to the satisfaction of the in- 
spection authorities. 

(3) The authority having jurisdiction shall be permitted to 
delegate to other qualified individuals such powers as 
necessary for the proper administration and enforce- 
ment of this Code. 

(4) Police, fire, and other enforcement agencies shall have 
authority to render necessary assistance in the en- 
forcement of this Code when requested to do so by the 
authority having jurisdiction. 

(5) The authority having jurisdiction shall be authorized 
to inspect, at all reasonable times, any building or 
premises for dangerous or hazardous conditions or 
equipment as set forth in this Code. The authority 
having jurisdiction shall be permitted to order any 
person(s) to remove or remedy such dangerous or haz- 
ardous condition or equipment. Any person(s) failing 
to comply with such order shall be in violation of this 
Code. 

(6) Where the authority having jurisdiction deems that 
conditions hazardous to life and property exist, he or 
she shall be permitted to require that such hazardous 
conditions in violation of this Code be corrected. 

(7) To the full extent permitted by law, any authority hav- 
ing jurisdiction engaged in inspection work shall be 
authorized at all reasonable times to enter and exam- 
ine any building, structure, or premises for the pur- 
pose of making electrical inspections. Before entering 
a premises, the authority having jurisdiction shall ob- 
tain the consent of the occupant thereof or obtain a 
court warrant authorizing entry for the purpose of in- 
spection except in those instances where an emer- 
gency exists. As used in this section, emergency 
means circumstances that the authority having juris- 
diction knows, or has reason to believe, exist and that 
reasonably can constitute immediate danger to per- 
sons or property. 

(8) Persons authorized to enter and inspect buildings, 
structures, and premises as herein set forth shall be 
identified by proper credentials issued by this govern- 
ing authority. 



(9) Persons shall not interfere with an authority having 
jurisdiction carrying out any duties or functions pre- 
scribed by this Code. 

(10) Persons shall not use a badge, uniform, or other cre- 
dentials to impersonate the authority having jurisdic- 
tion. 

(11) The authority having jurisdiction shall be permitted to 
investigate the cause, origin, and circumstances of any 
fire, explosion, or other hazardous condition. 

(12) The authority having jurisdiction shall be permitted to 
require plans and specifications to ensure compliance 
with this Code. 

(13) Whenever any installation subject to inspection prior 
to use is covered or concealed without having first 
been inspected, the authority having jurisdiction shall 
be permitted to require that such work be exposed for 
inspection. The authority having jurisdiction shall be 
notified when the installation is ready for inspection 
and shall conduct the inspection within days. 

(14) The authority having jurisdiction shall be permitted to 
order the immediate evacuation of any occupied 
building deemed unsafe when such building has haz- 
ardous conditions that present imminent danger to 
building occupants. 

(15) The authority having jurisdiction shall be permitted to 
waive specific requirements in this Code or permit 
alternative methods where it is assured that equivalent 
objectives can be achieved by establishing and main- 
taining effective safety. Technical documentation shall 
be submitted to the authority having jurisdiction to 
demonstrate equivalency and that the system, method, 
or device is approved for the intended purpose. 

(16) Each application for a waiver of a specific electrical 
requirement shall be filed with the authority having 
jurisdiction and shall be accompanied by such evi- 
dence, letters, statements, results of tests, or other sup- 
porting information as required to justify the request. 
The authority having jurisdiction shall keep a record 
of actions on such applications, and a signed copy of 
the authority having jurisdiction's decision shall be 
provided for the applicant. 

80.15 Electrical Board. 

(A) Creation of the Electrical Board. There is hereby 

created the Electrical Board of the of 

, hereinafter designated as the Board. 



(B) Appointments. Board members shall be appointed by 
the Governor with the advice and consent of the Senate (or 
by the Mayor with the advice and consent of the Council, 
or the equivalent). 

(1) Members of the Board shall be chosen in a manner to 
reflect a balanced representation of individuals or orga- 



2002 Edition 



NATIONAL ELECTRICAL CODE 



ARTICLE 80 — ADMINISTRATION AND ENFORCEMENT 



70-25 



nizations. The Chair of the Board shall be elected by 
the Board membership. 

(2) The Chief Electrical Inspector in the jurisdiction adopt- 
ing this Article authorized in 80.15(B)(3)(a) shall be 
the nonvoting secretary of the Board. Where the Chief 
Electrical Inspector of a local municipality serves a 
Board at a state level, he or she shall be permitted to 
serve as a voting member of the Board. 

(3) The board shall consist of not fewer than five voting 
members. Board members shall be selected from the 
following: 

a. Chief Electrical Inspector from a local government 
(for State Board only) 

b. An electrical contractor operating in the jurisdiction 

c. A licensed professional engineer engaged primarily 
in the design or maintenance of electrical installa- 
tions 

d. A journeyman electrician 

(4) Additional membership shall be selected from the fol- 
lowing: 

a. A master (supervising) electrician 

b. The Fire Marshal (or Fire Chief) 

c. A representative of the property /casualty insurance 
industry 

d. A representative of an electric power utility operat- 
ing in the jurisdiction 

e. A representative of electrical manufacturers prima- 
rily and actively engaged in producing materials, 
fittings, devices, appliances, luminaires (fixtures), or 
apparatus used as part of or in connection with elec- 
trical installations 

f. A member of the labor organization that represents 
the primary electrical workforce 

g. A member from the public who is not affiliated with 
any other designated group 

h. A representative of a telecommunications utility op- 
erating in the jurisdiction 

(C) Terms. Of the members first appointed, shall be 

appointed for a term of 1 year, for a term of 2 years, 

for a term of 3 years, and for a term of 4 

years, and thereafter each appointment shall be for a term 
of 4 years or until a successor is appointed. The Chair of 

the Board shall be appointed for a term not to exceed 

years. 

(D) Compensation. Each appointed member shall receive 

the sum of dollars ($ ) for each day during 

which the member attends a meeting of the Board and, in 
addition thereto, shall be reimbursed for direct lodging, 
travel, and meal expenses as covered by policies and pro- 
cedures established by the jurisdiction. 

(E) Quorum. A quorum as established by the Board oper- 
ating procedures shall be required to conduct Board busi- 



ness. The Board shall hold such meetings as necessary to 
carry out the purposes of Article 80. The Chair or a major- 
ity of the members of the Board shall have the authority to 
call meetings of the Board. 

(F) Duties. It shall be the duty of the Board to: 

(1) Adopt the necessary rules and regulations to administer 
and enforce Article 80. 

(2) Establish qualifications of electrical inspectors. 

(3) Revoke or suspend the recognition of any inspector's 
certificate for the jurisdiction. 

(4) After advance notice of the public hearings and the 
execution of such hearings, as established by law, the 
Board is authorized to establish and update the provi- 
sions for the safety of electrical installations to conform 
with the current edition of the National Electrical Code 
(NFPA 70) and other nationally recognized safety stan- 
dards for electrical installations. 

(5) Establish procedures for recognition of electrical safety 
standards and acceptance of equipment conforming to 
these standards. 

(G) Appeals. 

(1) Review of Decisions. Any person, firm, or corporation 
may register an appeal with the Board for a review of 
any decision of the Chief Electrical Inspector or of any 
Electrical Inspector, provided that such appeal is made 
in writing within fifteen (15) days after such person, 
firm, or corporation shall have been notified. Upon re- 
ceipt of such appeal, said Board shall, if requested by 
the person making the appeal, hold a public hearing 
and proceed to determine whether the action of the 
Board, or of the Chief Electrical Inspector, or of the 
Electrical Inspector complies with this law and, within 
fifteen (15) days after receipt of the appeal or after 
holding the hearing, shall make a decision in accor- 
dance with its findings. 

(2) Conditions. Any person shall be permitted to appeal a 
decision of the authority having jurisdiction to the 
Board when it is claimed that any one or more of the 
following conditions exist: 

a. The true intent of the codes or ordinances described 
in this Code has been incorrectly interpreted. 

b. The provisions of the codes or ordinances do not 
fully apply. 

c. A decision is unreasonable or arbitrary as it applies 
to alternatives or new materials. 

(3) Submission of Appeals. A written appeal, outlining the 
Code provision from which relief is sought and the 
remedy proposed, shall be submitted to the authority 
having jurisdiction within 15 calendar days of notifica- 
tion of violation. 



NATIONAL ELECTRICAL CODE 



2002 Edition 



70-26 



ARTICLE 80 — ADMINISTRATION AND ENFORCEMENT 



(H) Meetings and Records. Meetings and records of the 
Board shall conform to the following: 

(1) Meetings of the Board shall be open to the public as 
required by law. 

(2) Records of meetings of the Board shall be available for 
review during normal business hours, as required by 
law. 

80.17 Records and Reports. The authority having juris- 
diction shall retain records in accordance with 80.17(A) 
and (B). 

(A) Retention. The authority having jurisdiction shall 
keep a record of all electrical inspections, including the 
date of such inspections and a summary of any violations 
found to exist, the date of the services of notices, and a 
record of the final disposition of all violations. All required 
records shall be maintained until their usefulness has been 
served or as otherwise required by law. 

(B) Availability. A record of examinations, approvals, and 
variances granted shall be maintained by the authority hav- 
ing jurisdiction and shall be available for public review as 
prescribed by law during normal business hours. 

80.19 Permits and Approvals. Permits and approvals 
shall conform to 80.19(A) through (H). 

(A) Application. 

(1) Activity authorized by a permit issued under this Code 
shall be conducted by the permittee or the permittee's 
agents or employees in compliance with all require- 
ments of this Code applicable thereto and in accor- 
dance with the approved plans and specifications. No 
permit issued under this Code shall be interpreted to 
justify a violation of any provision of this Code or any 
other applicable law or regulation. Any addition or al- 
teration of approved plans or specifications shall be 
approved in advance by the authority having jurisdic- 
tion, as evidenced by the issuance of a new or amended 
permit. 

(2) A copy of the permit shall be posted or otherwise 
readily accessible at each work site or carried by the 
permit holder as specified by the authority having 
jurisdiction. 

(B) Content. Permits shall be issued by the authority hav- 
ing jurisdiction and shall bear the name and signature of the 
authority having jurisdiction or that of the authority having 
jurisdiction's designated representative. In addition, the 
permit shall indicate the following: 

(1) Operation or activities for which the permit is issued 

(2) Address or location where the operation or activity is to 
be conducted 



(3) Name and address of the permittee 

(4) Permit number and date of issuance 

(5) Period of validity of the permit 

(6) Inspection requirements 

(C) Issuance of Permits. The authority having jurisdiction 
shall be authorized to establish and issue permits, certifi- 
cates, notices, and approvals, or orders pertaining to elec- 
trical safety hazards pursuant to 80.23, except that no per- 
mit shall be required to execute any of the classes of 
electrical work specified in the following: 

(1) Installation or replacement of equipment such as lamps 
and of electric utilization equipment approved for con- 
nection to suitable permanently installed receptacles. 
Replacement of flush or snap switches, fuses, lamp 
sockets, and receptacles, and other minor maintenance 
and repair work, such as replacing worn cords and 
tightening connections on a wiring device 

(2) The process of manufacturing, testing, servicing, or re- 
pairing electric equipment or apparatus 

(D) Annual Permits. In lieu of an individual permit for 
each installation or alteration, an annual permit shall, upon 
application, be issued to any person, firm, or corporation 
regularly employing one or more employees for the instal- 
lation, alteration, and maintenance of electric equipment in 
or on buildings or premises owned or occupied by the ap- 
plicant for the permit. Upon application, an electrical con- 
tractor as agent for the owner or tenant shall be issued an 
annual permit. The applicant shall keep records of all work 
done, and such records shall be transmitted periodically to 
the Electrical Inspector. 

(E) Fees. Any political subdivision that has been provided 
for electrical inspection in accordance with the provisions 
of Article 80 may establish fees that shall be paid by the 
applicant for a permit before the permit is issued. 

(F) Inspection and Approvals. 

(1) Upon the completion of any installation of electrical 
equipment that has been made under a permit other 
than an annual permit, it shall be the duty of the person, 
firm, or corporation making the installation to notify 
the Electrical Inspector having jurisdiction, who shall 
inspect the work within a reasonable time. 

(2) Where the Inspector finds the installation to be in con- 
formity with the statutes of all applicable local ordi- 
nances and all rules and regulations, the Inspector shall 
issue to the person, firm, or corporation making the 
installation a certificate of approval, with duplicate 
copy for delivery to the owner, authorizing the connec- 
tion to the supply of electricity and shall send written 
notice of such authorization to the supplier of electric 
service. When a certificate of temporary approval is 



• 



2002 Edition 



NATIONAL ELECTRICAL CODE 



ARTICLE 80 — ADMINISTRATION AND ENFORCEMENT 



70-27 



issued authorizing the connection of an installation, 
such certificates shall be issued to expire at a time to be 
stated therein and shall be revocable by the Electrical 
Inspector for cause. 

(3) When any portion of the electrical installation within 
the jurisdiction of an Electrical Inspector is to be hid- 
den from view by the permanent placement of parts of 
the building, the person, firm, or corporation installing 
the equipment shall notify the Electrical Inspector, and 
such equipment shall not be concealed until it has been 

approved by the Electrical Inspector or until 

days have elapsed from the time of such notification, 
provided that on large installations, where the conceal- 
ment of equipment proceeds continuously, the person, 
firm, or corporation installing the equipment shall give 
the Electrical Inspector due notice in advance, and in- 
spections shall be made periodically during the 
progress of the work. 

(4) At regular intervals, the Electrical Inspector having ju- 
risdiction shall visit all buildings and premises where 
work may be done under annual permits and shall in- 
spect all electric equipment installed under such per- 
mits since the date of the previous inspection. The 
Electrical Inspector shall issue a certificate of approval 
for such work as is found to be in conformity with the 
provisions of Article 80 and all applicable ordinances, 
orders, rules, and regulations, after payments of all re- 
quired fees. 

(5) If, upon inspection, any installation is found not to be 
fully in conformity with the provisions of Article 80, 
and all applicable ordinances, rules, and regulations, 
the Inspector making the inspection shall at once for- 
ward to the person, firm, or corporation making the 
installation a written notice stating the defects that have 
been found to exist. 

(G) Revocation of Permits. Revocation of permits shall 
conform to the following: 



(1) The authority having jurisdiction shall be permitted to 
revoke a permit or approval issued if any violation of 
this Code is found upon inspection or in case there 
have been any false statements or misrepresentations 
submitted in the application or plans on which the per- 
mit or approval was based. 

(2) Any attempt to defraud or otherwise deliberately or 
knowingly design, install, service, maintain, operate, 
sell, represent for sale, falsify records, reports, or ap- 
plications, or other related activity in violation of the 
requirements prescribed by this Code shall be a viola- 
tion of this Code. Such violations shall be cause for 
immediate suspension or revocation of any related li- 
censes, certificates, or permits issued by this jurisdic- 
tion. In addition, any such violation shall be subject to 



any other criminal or civil penalties as available by the 
laws of this jurisdiction. 

(3) Revocation shall be constituted when the permittee is 
duly notified by the authority having jurisdiction. 

(4) Any person who engages in any business, operation, or 
occupation, or uses any premises, after the permit is- 
sued therefor has been suspended or revoked pursuant 
to the provisions of this Code, and before such sus- 
pended permit has been reinstated or a new permit is- 
sued, shall be in violation of this Code. 

(5) A permit shall be predicated upon compliance with the 
requirements of this Code and shall constitute written 
authority issued by the authority having jurisdiction to 
install electrical equipment. Any permit issued under 
this Code shall not take the place of any other license 
or permit required by other regulations or laws of this 
jurisdiction. 

(6) The authority having jurisdiction shall be permitted to 
require an inspection prior to the issuance of a permit. 

(7) A permit issued under this Code shall continue until 
revoked or for the period of time designated on the 
permit. The permit shall be issued to one person or 
business only and for the location or purpose described 
in the permit. Any change that affects any of the con- 
ditions of the permit shall require a new or amended 
permit. 

(H) Applications and Extensions. Applications and ex- 
tensions of permits shall conform to the following: 



(1) The authority having jurisdiction shall be permitted to 
grant an extension of the permit time period upon pre- 
sentation by the permittee of a satisfactory reason for 
failure to start or complete the work or activity autho- 
rized by the permit. 

(2) Applications for permits shall be made to the authority 
having jurisdiction on forms provided by the jurisdic- 
tion and shall include the applicant's answers in full to 
inquiries set forth on such forms. Applications for per- 
mits shall be accompanied by such data as required by 
the authority having jurisdiction, such as plans and 
specifications, location, and so forth. Fees shall be de- 
termined as required by local laws. 

(3) The authority having jurisdiction shall review all appli- 
cations submitted and issue permits as required. If an 
application for a permit is rejected by the authority 
having jurisdiction, the applicant shall be advised of 
the reasons for such rejection. Permits for activities 
requiring evidence of financial responsibility by the ju- 
risdiction shall not be issued unless proof of required 
financial responsibility is furnished. 

80.21 Plans Review. Review of plans and specifications 
shall conform to 80.21(A) through (C). 



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ARTICLE 80 — ADMINISTRATION AND ENFORCEMENT 



(A) Authority. For new construction, modification, or re- 
habilitation, the authority having jurisdiction shall be per- 
mitted to review construction documents and drawings. 

(B) Responsibility of the Applicant. It shall be the re- 
sponsibility of the applicant to ensure the following: 

(1) The construction documents include all of the electrical 
requirements. 

(2) The construction documents and drawings are correct 
and in compliance with the applicable codes and 
standards. 

(C) Responsibility of the Authority Having Jurisdiction. 

It shall be the responsibility of the authority having juris- 
diction to promulgate rules that cover the following: 

(1) Review of construction documents and drawings within 
established time frames for the purpose of acceptance 
or to provide reasons for nonacceptance 

(2) Review and approval by the authority having jurisdic- 
tion shall not relieve the applicant of the responsibility 
of compliance with this Code. 

(3) Where field conditions necessitate any substantial 
change from the approved plan, the authority having 
jurisdiction shall be permitted to require that the cor- 
rected plans be submitted for approval. 

80.23 Notice of Violations, Penalties. Notice of violations 
and penalties shall conform to 80.23(A) and (B). 

(A) Violations. 



(1) Whenever the authority having jurisdiction determines 
that there are violations of this Code, a written notice 
shall be issued to confirm such findings. 

(2) Any order or notice issued pursuant to this Code shall 
be served upon the owner, operator, occupant, or other 
person responsible for the condition or violation, either 
by personal service or mail or by delivering the same 
to, and leaving it with, some person of responsibility 
upon the premises. For unattended or abandoned loca- 
tions, a copy of such order or notice shall be posted on 
the premises in a conspicuous place at or near the en- 
trance to such premises and the order or notice shall be 
mailed by registered or certified mail, with return re- 
ceipt requested, to the last known address of the owner, 
occupant, or both. 

(B) Penalties. 

(1) Any person who fails to comply with the provisions of 
this Code or who fails to carry out an order made pur- 
suant to this Code or violates any condition attached to 
a permit, approval, or certificate shall be subject to the 
penalties established by this jurisdiction. 

(2) Failure to comply with the time limits of an abatement 
notice or other corrective notice issued by the authority 



having jurisdiction shall result in each day that such 
violation continues being regarded as a new and sepa- 
rate offense. 
(3) Any person, firm, or corporation who shall willfully 
violate any of the applicable provisions of this article 
shall be guilty of a misdemeanor and, upon conviction 
thereof, shall be punished by a fine of not less than 
dollars ($ ) or more than dollars 



($. 



_) for each offense, together with the costs of 



prosecution, imprisonment, or both, for not less than 
( ) days or more than 



C 



_) days. 



80.25 Connection to Electricity Supply. Connections to 
the electric supply shall conform to 80.25(A) through (E). 

(A) Authorization. Except where work is done under an 
annual permit and except as otherwise provided in 80.25, it 
shall be unlawful for any person, firm, or corporation to 
make connection to a supply of electricity or to supply 
electricity to any electric equipment installation for which a 
permit is required or that has been disconnected or ordered 
to be disconnected. 

(B) Special Consideration. By special permission of the 
authority having jurisdiction, temporary power shall be per- 
mitted to be supplied to the premises for specific needs of 
the construction project. The Board shall determine what 
needs are permitted under this provision. 



(C) Notification. If, within 



business days after the 



Electrical Inspector is notified of the completion of an in- 
stallation of electric equipment, other than a temporary ap- 
proval installation, the Electrical Inspector has neither au- 
thorized connection nor disapproved the installation, the 
supplier of electricity is authorized to make connections 
and supply electricity to such installation. 

(D) Other Territories. If an installation or electric equip- 
ment is located in any territory where an Electrical Inspec- 
tor has not been authorized or is not required to make 
inspections, the supplier of electricity is authorized to make 
connections and supply electricity to such installations. 

(E) Disconnection. Where a connection is made to an in- 
stallation that has not been inspected, as outlined in the 
preceding paragraphs of this section, the supplier of elec- 
tricity shall immediately report such connection to the 
Chief Electrical Inspector. If, upon subsequent inspection, it 
is found that the installation is not in conformity with the 
provisions of Article 80, the Chief Electrical Inspector shall 
notify the person, firm, or corporation making the installa- 
tion to rectify the defects and, if such work is not com- 
pleted within fifteen (15) business days or a longer period 
as may be specified by the Board, the Board shall have the 



# 



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ARTICLE 90 — INTRODUCTION 



70-29 



authority to cause the disconnection of that portion of the 
installation that is not in conformity. 

80.27 Inspector's Qualifications. 

(A) Certificate. All electrical inspectors shall be certified 
by a nationally recognized inspector certification program 
accepted by the Board. The certification program shall spe- 
cifically qualify the inspector in electrical inspections. No 
person shall be employed as an Electrical Inspector unless 
that person is the holder of an Electrical Inspector's certifi- 
cate of qualification issued by the Board, except that any 
person who on the date on which this law went into effect 
was serving as a legally appointed Electrical Inspector of 
shall, upon application and payment of the pre- 
scribed fee and without examination, be issued a special 
certificate permitting him or her to continue to serve as an 
Electrical Inspector in the same territory. 

(B) Experience. Electrical inspector applicants shall dem- 
onstrate the following: 

(1) Have a demonstrated knowledge of the standard mate- 
rials and methods used in the installation of electric 
equipment 

(2) Be well versed in the approved methods of construction 
for safety to persons and property 
Be well versed in the statutes of relating to 



(3) 



(4) 



electrical work and the National Electrical Code, as 
approved by the American National Standards Institute 
Have had at least years' experience as an Electri- 
cal Inspector or years in the installation of elec- 
trical equipment. In lieu of such experience, the appli- 
cant shall be a graduate in electrical engineering or of a 
similar curriculum of a college or university considered 
by the Board as having suitable requirements for gradu- 
ation and shall have had two years' practical electrical 
experience. 



(C) Recertification. Electrical inspectors shall be recerti- 
fied as established by provisions of the applicable certifica- 
tion program. 

(D) Revocation and Suspension of Authority. The Board 
shall have the authority to revoke an inspector's authority 
to conduct inspections within a jurisdiction. 

80.29 Liability for Damages. Article 80 shall not be con- 
strued to affect the responsibility or liability of any party 
owning, designing, operating, controlling, or installing any 
electric equipment for damages to persons or property 

caused by a defect therein, nor shall the or any of its 

employees be held as assuming any such liability by reason 
of the inspection, reinspection, or other examination autho- 
rized. 



80.31 Validity. If any section, subsection, sentence, clause, 
or phrase of Article 80 is for any reason held to be uncon- 
stitutional, such decision shall not affect the validity of the 
remaining portions of Article 80. 

80.33 Repeal of Conflicting Acts. All acts or parts of acts 
in conflict with the provisions of Article 80 are hereby 
repealed. 

80.35 Effective Date. Article 80 shall take effect 
( ) days after its passage and publica- 
tion. 



90.1 Purpose. 

(A) Practical Safeguarding. The purpose of this Code is 
the practical safeguarding of persons and property from 
hazards arising from the use of electricity. 

(B) Adequacy. This Code contains provisions that are con- 
sidered necessary for safety. Compliance therewith and 
proper maintenance will result in an installation that is es- 
sentially free from hazard but not necessarily efficient, con- 
venient, or adequate for good service or future expansion of 
electrical use. 

FPN: Hazards often occur because of overloading of wir- 
ing systems by methods or usage not in conformity with 
this Code. This occurs because initial wiring did not pro- 
vide for increases in the use of electricity. An initial ad- 
equate installation and reasonable provisions for system 
changes will provide for future increases in the use of 
electricity. 

(C) Intention. This Code is not intended as a design speci- 
fication or an instruction manual for untrained persons. 

(D) Relation to International Standards. The require- 
ments in this Code address the fundamental principles of 
protection for safety contained in Section 131 of Interna- 
tional Electrotechnical Commission Standard 60364-1, 
Electrical Installations of Buildings. 

FPN: IEC 60364-1, Section 131, contains fundamental 
principles of protection for safety that encompass protec- 
tion against electric shock, protection against thermal ef- 
fects, protection against overcurrent, protection against 
fault currents, and protection against overvoltage. All of 
these potential hazards are addressed by the requirements in 
this Code. 

90.2 Scope. 

(A) Covered. This Code covers the installation of electric 
conductors, electric equipment, signaling and communica- 



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ARTICLE 90 — INTRODUCTION 



tions conductors and equipment, and fiber optic cables and 
raceways for the following: 

(1) Public and private premises, including buildings, struc- 
tures, mobile homes, recreational vehicles, and floating 
buildings 

(2) Yards, lots, parking lots, carnivals, and industrial sub- 
stations 

FPN: For additional information concerning such installa- 
tions in an industrial or multibuilding complex, see ANSI 
C2-1997, National Electrical Safety Code. 

(3) Installations of conductors and equipment that connect 
to the supply of electricity 

(4) Installations used by the electric utility, such as office 
buildings, warehouses, garages, machine shops, and 
recreational buildings, that are not an integral part of a 
generating plant, substation, or control center 

(B) Not Covered. This Code does not cover the following: 

(1) Installations in ships, watercraft other than floating 
buildings, railway rolling stock, aircraft, or automotive 
vehicles other than mobile homes and recreational ve- 
hicles 

FPN: Although the scope of this Code indicates that the 
Code does not cover installations in ships, portions of this 
Code are incorporated by reference into Title 46, Code of 
Federal Regulations, Parts 110-113. 

(2) Installations under ground in mines and self-propelled 
mobile surface mining machinery and its attendant 
electrical trailing cable 

(3) Installations of railways for generation, transformation, 
transmission, or distribution of power used exclusively 
for operation of rolling stock or installations used ex- 
clusively for signaling and communications purposes 

(4) Installations of communications equipment under the 
exclusive control of communications utilities located 
outdoors or in building spaces used exclusively for 
such installations 

Installations under the exclusive control of an electric 
utility where such installations 

a. Consist of service drops or service laterals, and as- 
sociated metering, or 

b. Are located in legally established easements, rights- 
of-way, or by other agreements either designated by 
or recognized by public service commissions, utility 
commissions, or other regulatory agencies having 
jurisdiction for such installations, or 

c. Are on property owned or leased by the electric 
utility for the purpose of communications, metering, 
generation, control, transformation, transmission, or 
distribution of electric energy. 



(5) 



(C) Special Permission. The authority having jurisdiction 
for enforcing this Code may grant exception for the instal- 



lation of conductors and equipment that are not under the 
exclusive control of the electric utilities and are used to 
connect the electric utility supply system to the service- 
entrance conductors of the premises served, provided such 
installations are outside a building or terminate immedi- 
ately inside a building wall. 

90.3 Code Arrangement. This Code is divided into the 
introduction and nine chapters, as shown in Figure 90.3. 
Chapters 1, 2, 3, and 4 apply generally; Chapters 5, 6 and 7 
apply to special occupancies, special equipment, or other 
special conditions. These latter chapters supplement or 
modify the general rules. Chapters 1 through 4 apply except 
as amended by Chapters 5, 6, and 7 for the particular con- 
ditions. 

Chapter 8 covers communications systems and is not 
subject to the requirements of Chapters 1 through 7 except 
where the requirements are specifically referenced in Chap- 
ter 8. 

Chapter 9 consists of tables. 

Annexes are not part of the requirements of this Code 
but are included for informational purposes only. 



Chapter 1 — General 



Chapter 2 — Wiring and Protection 



Chapter 3 — Wiring Methods and Materials 



Chapter 4 — Equipment for General Use 



Applies generally 

to all electrical 

installations 



Supplements or modifies 
Chapters 1 through 4 



Chapter 5 — Special Occupancies 



Chapter 6 — Special Equipment 



Chapter 7 — Special Conditions 



Chapter 8 is not subject to 
the requirements of 



T 7 H Chapters 1 through 7 except 

Chapter 8 — Communications Systems| r 



where the requirements are 
specifically referenced in 
Chapter 8. 



Chapter 9 — Tables 



Annex A through Annex F 



i- Applicable as referenced 
~|| Informational only; 



not mandatory 



Figure 90.3 Code arrangement. 



90.4 Enforcement. This Code is intended to be suitable 
for mandatory application by governmental bodies that ex- 
ercise legal jurisdiction over electrical installations, includ- 
ing signaling and communications systems, and for use by 
insurance inspectors. The authority having jurisdiction for 
enforcement of the Code has the responsibility for making 
interpretations of the rules, for deciding on the approval of 



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ARTICLE 90 — INTRODUCTION 



70-31 



equipment and materials, and for granting the special per- 
mission contemplated in a number of the rules. 

By special permission, the authority having jurisdiction 
may waive specific requirements in this Code or permit 
alternative methods where it is assured that equivalent ob- 
jectives can be achieved by establishing and maintaining 
effective safety. 

This Code may require new products, constructions, or 
materials that may not yet be available at the time the Code 
is adopted. In such event, the authority having jurisdiction 
may permit the use of the products, constructions, or mate- 
rials that comply with the most recent previous edition of 
this Code adopted by the jurisdiction. 

90.5 Mandatory Rules, Permissive Rules, and Explana- 
tory Material. 

(A) Mandatory Rules. Mandatory rules of this Code are 
those that identify actions that are specifically required or 
prohibited and are characterized by the use of the terms 
shall or shall not. 

(B) Permissive Rules. Permissive rules of this Code are 
those that identify actions that are allowed but not required, 
are normally used to describe options or alternative meth- 
ods, and are characterized by the use of the terms shall be 
permitted or shall not be required. 

(C) Explanatory Material. Explanatory material, such as 
references to other standards, references to related sections 
of this Code, or information related to a Code rule, is in- 
cluded in this Code in the form of fine print notes (FPNs). 
Fine print notes are informational only and are not enforce- 
able as requirements of this Code. 

FPN: The format and language used in this Code follows 
guidelines established by NFPA and published in the NEC 
Style Manual. Copies of this manual can be obtained from 
NFPA. 

90.6 Formal Interpretations. To promote uniformity of 
interpretation and application of the provisions of this 
Code, formal interpretation procedures have been estab- 
lished and are found in the NFPA Regulations Governing 
Committee Projects. 

90.7 Examination of Equipment for Safety. For specific 
items of equipment and materials referred to in this Code, 
examinations for safety made under standard conditions 
provide a basis for approval where the record is made gen- 
erally available through promulgation by organizations 
properly equipped and qualified for experimental testing, 
inspections of the run of goods at factories, and service- 
value determination through field inspections. This avoids 
the necessity for repetition of examinations by different 
examiners, frequently with inadequate facilities for such 



work, and the confusion that would result from conflicting 
reports on the suitability of devices and materials examined 
for a given purpose. 

It is the intent of this Code that factory-installed inter- 
nal wiring or the construction of equipment need not be 
inspected at the time of installation of the equipment, ex- 
cept to detect alterations or damage, if the equipment has 
been listed by a qualified electrical testing laboratory that is 
recognized as having the facilities described in the preced- 
ing paragraph and that requires suitability for installation in 
accordance with this Code. 



FPN No. 1 
FPN No. 2 
FPN No. 3 



See requirements in 110.3. 

Listed is defined in Article 100. 

Annex A contains an informative list of prod- 



uct safety standards for electrical equipment. 

90.8 Wiring Planning. 

(A) Future Expansion and Convenience. Plans and 
specifications that provide ample space in raceways, spare 
raceways, and additional spaces allow for future increases 
in the use of electricity. Distribution centers located in 
readily accessible locations provide convenience and safety 
of operation. 

(B) Number of Circuits in Enclosures. It is elsewhere 
provided in this Code that the number of wires and circuits 
confined in a single enclosure be varyingly restricted. Lim- 
iting the number of circuits in a single enclosure minimizes 
the effects from a short circuit or ground fault in one cir- 
cuit. 

90.9 Units of Measurement. 

(A) Measurement System of Preference. For the purpose 
of this Code, metric units of measurement are in accor- 
dance with the modernized metric system known as the 
International System of Units (SI). 

(B) Dual System of Units. The SI units shall appear first, 
and the inch-pound units shall immediately follow in pa- 
rentheses. The conversion from the inch-pound units to SI 
units shall be based on hard conversion except as provided 
in 90.9(C). 

(C) Permitted Uses of Soft Conversion. The cases given 
in 90.9(C)(1) through (4) shall not be required to use hard 
conversion and shall be permitted to use soft conversion. 

(1) Trade Sizes. Where the actual measured size of a prod- 
uct is not the same as the nominal size, trade size designa- 
tors shall be used rather than dimensions. Trade practices 
shall be followed in all cases. 

(2) Extracted Material. Where material is extracted from 
another standard, the context of the original material shall 



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70-32 



ARTICLE 90 — INTRODUCTION 



not be compromised or violated. Any editing of the ex- 
tracted text shall be confined to making the style consistent 
with that of the NEC. 

(3) Industry Practice. Where industry practice is to ex- 
press units in inch-pound units, the inclusion of SI units 
shall not be required. 

(4) Safety. Where a negative impact on safety would result, 
hard conversion shall not be required. 

(D) Compliance. The conversion from inch-pound units to 
SI units shall be permitted to be an approximate conver- 
sion. Compliance with the numbers shown in either the SI 



system or the inch-pound system shall constitute compli- 
ance with this Code. 

FPN No. 1: Hard conversion is considered a change in 
dimensions or properties of an item into new sizes that 
might or might not be interchangeable with the sizes used 
in the original measurement. Soft conversion is considered 
a direct mathematical conversion and involves a change in 
the description of an existing measurement but not in the 
actual dimension. 

FPN No. 2: SI conversions are based on IEEE/ASTM SI 
10-1997, Standard for the Use of the International System 
of Units (SI): The Modern Metric System. 



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ARTICLE 100 — DEFINITIONS 



70-33 



Chapter 1 General 



ARTICLE 100 
Definitions 



• 



Scope. This article contains only those definitions essential 
to the proper application of this Code. It is not intended to 
include commonly defined general terms or commonly de- 
fined technical terms from related codes and standards. In 
general, only those terms that are used in two or more 
articles are defined in Article 100. Other definitions are 
included in the article in which they are used but may be 
referenced in Article 100. 

Part I of this article contains definitions intended to 
apply wherever the terms are used throughout this Code. 
Part II contains definitions applicable only to the parts of 
articles specifically covering installations and equipment 
operating at over 600 volts, nominal. 

I. General 

Accessible (as applied to equipment). Admitting close 
approach; not guarded by locked doors, elevation, or other 
effective means. 

Accessible (as applied to wiring methods). Capable of 
being removed or exposed without damaging the building 
structure or finish or not permanently closed in by the struc- 
ture or finish of the building. 

Accessible, Readily (Readily Accessible). Capable of be- 
ing reached quickly for operation, renewal, or inspections 
without requiring those to whom ready access is requisite 
to climb over or remove obstacles or to resort to portable 
ladders, and so forth. 

Ampacity. The current, in amperes, that a conductor can 
carry continuously under the conditions of use without ex- 
ceeding its temperature rating. 

Appliance. Utilization equipment, generally other than in- 
dustrial, that is normally built in standardized sizes or types 
and is installed or connected as a unit to perform one or 
more functions such as clothes washing, air conditioning, 
food mixing, deep frying, and so forth. 

Approved. Acceptable to the authority having jurisdiction. 

Askarel. A generic term for a group of nonflammable syn- 
thetic chlorinated hydrocarbons used as electrical insulating 
media. Askarels of various compositional types are used. 
Under arcing conditions, the gases produced, while consist- 
ing predominantly of noncombustible hydrogen chloride, 



can include varying amounts of combustible gases, depend- 
ing on the askarel type. 

Attachment Plug (Plug Cap) (Plug). A device that, by 
insertion in a receptacle, establishes a connection between 
the conductors of the attached flexible cord and the conduc- 
tors connected permanently to the receptacle. 

Authority Having Jurisdiction. The organization, office, 
or individual responsible for approving equipment, materi- 
als, an installation, or a procedure. 

FPN: The phrase "authority having jurisdiction" is used in 
NFPA documents in a broad manner, since jurisdictions and 
approval agencies vary, as do their responsibilities. Where 
public safety is primary, the authority having jurisdiction 
may be a federal, state, local, or other regional department 
or individual such as a fire chief; fire marshal; chief of a fire 
prevention bureau, labor department, or health department; 
building official; electrical inspector; or others having statu- 
tory authority. For insurance purposes, an insurance inspec- 
tion department, rating bureau, or other insurance company 
representative may be the authority having jurisdiction. In 
many circumstances, the property owner or his or her des- 
ignated agent assumes the role of the authority having ju- 
risdiction; at government installations, the commanding of- 
ficer or departmental official may be the authority having 
jurisdiction. 

Automatic. Self-acting, operating by its own mechanism 
when actuated by some impersonal influence, as, for ex- 
ample, a change in current, pressure, temperature, or me- 
chanical configuration. 

Bathroom. An area including a basin with one or more of 
the following: a toilet, a tub, or a shower. 

Bonding (Bonded). The permanent joining of metallic 
parts to form an electrically conductive path that ensures 
electrical continuity and the capacity to conduct safely any 
current likely to be imposed. 

Bonding Jumper. A reliable conductor to ensure the re- 
quired electrical conductivity between metal parts required 
to be electrically connected. 

Bonding Jumper, Equipment. The connection between 
two or more portions of the equipment grounding conduc- 
tor. 

Bonding Jumper, Main. The connection between the 
grounded circuit conductor and the equipment grounding 
conductor at the service. 

Branch Circuit. The circuit conductors between the final 
overcurrent device protecting the circuit and the outlet(s). 

Branch Circuit, Appliance. A branch circuit that supplies 
energy to one or more outlets to which appliances are to be 



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70-34 



ARTICLE 100 — DEFINITIONS 



connected and that has no permanently connected lumi- 
naires (lighting fixtures) that are not a part of an appliance. 

Branch Circuit, General-Purpose. A branch circuit that 
supplies two or more receptacles or outlets for lighting and 
appliances. 

Branch Circuit, Individual. A branch circuit that supplies 
only one utilization equipment. 

Branch Circuit, Multiwire. A branch circuit that consists 
of two or more ungrounded conductors that have a voltage 
between them, and a grounded conductor that has equal 
voltage between it and each ungrounded conductor of the 
circuit and that is connected to the neutral or grounded 
conductor of the system. 

Building. A structure that stands alone or that is cut off 
from adjoining structures by fire walls with all openings 
therein protected by approved fire doors. 

Cabinet. An enclosure that is designed for either surface 
mounting or flush mounting and is provided with a frame, 
mat, or trim in which a swinging door or doors are or can 
be hung. 

Circuit Breaker. A device designed to open and close a 
circuit by nonautomatic means and to open the circuit au- 
tomatically on a predetermined overcurrent without damage 
to itself when properly applied within its rating. 

FPN: The automatic opening means can be integral, direct 
acting with the circuit breaker, or remote from the circuit 
breaker. 

Adjustable (as applied to circuit breakers). A qualifying 
term indicating that the circuit breaker can be set to trip at 
various values of current, time, or both, within a predeter- 
mined range. 

Instantaneous Trip (as applied to circuit breakers). A 
qualifying term indicating that no delay is purposely intro- 
duced in the tripping action of the circuit breaker. 

Inverse Time (as applied to circuit breakers). A qualifying 
term indicating that there is purposely introduced a delay in 
the tripping action of the circuit breaker, which delay de- 
creases as the magnitude of the current increases. 

Nonadjustable (as applied to circuit breakers). A qualify- 
ing term indicating that the circuit breaker does not have 
any adjustment to alter the value of current at which it will 
trip or the time required for its operation. 

Setting (of circuit breakers). The value of current, time, or 
both, at which an adjustable circuit breaker is set to trip. 

Concealed. Rendered inaccessible by the structure or finish 
of the building. Wires in concealed raceways are consid- 
ered concealed, even though they may become accessible 
by withdrawing them. 



Conductor, Bare. A conductor having no covering or elec- 
trical insulation whatsoever. 

Conductor, Covered. A conductor encased within material 
of composition or thickness that is not recognized by this 
Code as electrical insulation. 

Conductor, Insulated. A conductor encased within mate- 
rial of composition and thickness that is recognized by this 
Code as electrical insulation. 

Conduit Body. A separate portion of a conduit or tubing 
system that provides access through a removable cover(s) 
to the interior of the system at a junction of two or more 
sections of the system or at a terminal point of the system. 
Boxes such as FS and FD or larger cast or sheet metal 
boxes are not classified as conduit bodies. 

Connector, Pressure (Solderless). A device that estab- 
lishes a connection between two or more conductors or 
between one or more conductors and a terminal by means 
of mechanical pressure and without the use of solder. 

Continuous Load. A load where the maximum current is 
expected to continue for 3 hours or more. 

Controller. A device or group of devices that serves to 
govern, in some predetermined manner, the electric power 
delivered to the apparatus to which it is connected. 

Cooking Unit, Counter-Mounted. A cooking appliance 
designed for mounting in or on a counter and consisting of 
one or more heating elements, internal wiring, and built-in 
or mountable controls. 

Copper-Clad Aluminum Conductors. Conductors drawn 
from a copper-clad aluminum rod with the copper metallur- 
gically bonded to an aluminum core. The copper forms a 
minimum of 10 percent of the cross-sectional area of a 
solid conductor or each strand of a stranded conductor. 

Cutout Box. An enclosure designed for surface mounting 
that has swinging doors or covers secured directly to and 
telescoping with the walls of the box proper. 

Dead Front. Without live parts exposed to a person on the 
operating side of the equipment. 

Demand Factor. The ratio of the maximum demand of a 
system, or part of a system, to the total connected load of a 
system or the part of the system under consideration. 

Device. A unit of an electrical system that is intended to 
carry but not utilize electric energy. 

Disconnecting Means. A device, or group of devices, or 
other means by which the conductors of a circuit can be 
disconnected from their source of supply. 

Dusttight. Constructed so that dust will not enter the en- 
closing case under specified test conditions. 



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ARTICLE 100 — DEFINITIONS 



70-35 



• 



Duty, Continuous. Operation at a substantially constant 
load for an indefinitely long time. 

Duty, Intermittent. Operation for alternate intervals of 
(1) load and no load; or (2) load and rest; or (3) load, no 
load, and rest. 

Duty, Periodic. Intermittent operation in which the load 
conditions are regularly recurrent. 

Duty, Short-Time. Operation at a substantially constant 
load for a short and definite, specified time. 

Duty, Varying. Operation at loads, and for intervals of 
time, both of which may be subject to wide variation. 

Dwelling Unit. One or more rooms for the use of one or 
more persons as a housekeeping unit with space for eating, 
living, and sleeping, and permanent provisions for cooking 
and sanitation. 

Dwelling, One-Family. A building that consists solely of 
one dwelling unit. 

Dwelling, Two-Family. A building that consists solely of 
two dwelling units. 

Dwelling, Multifamily. A building that contains three or 
more dwelling units. 

Electric Sign. A fixed, stationary, or portable self- 
contained, electrically illuminated utilization equipment 
with words or symbols designed to convey information or 
attract attention. 

Enclosed. Surrounded by a case, housing, fence, or wall(s) 
that prevents persons from accidentally contacting ener- 
gized parts. 

Enclosure. The case or housing of apparatus, or the fence 
or walls surrounding an installation to prevent personnel 
from accidentally contacting energized parts or to protect 
the equipment from physical damage. 

FPN: See Table 430.91 for examples of enclosure types. 

Energized. Electrically connected to a source of voltage. 

Equipment. A general term including material, fittings, de- 
vices, appliances, luminaires (fixtures), apparatus, and the 
like used as a part of, or in connection with, an electrical 
installation. 

Explosionproof Apparatus. Apparatus enclosed in a case 
that is capable of withstanding an explosion of a specified 
gas or vapor that may occur within it and of preventing the 
ignition of a specified gas or vapor surrounding the enclo- 
sure by sparks, flashes, or explosion of the gas or vapor 
within, and that operates at such an external temperature 
that a surrounding flammable atmosphere will not be ig- 
nited thereby. 



FPN: For further information, see ANSI/UL 1203-1999, 
Explosion-Proof and Dust-Ignition-Proof Electrical Equip- 
ment for Use in Hazardous (Classified) Locations. 

Exposed (as applied to live parts). Capable of being in- 
advertently touched or approached nearer than a safe dis- 
tance by a person. It is applied to parts that are not suitably 
guarded, isolated, or insulated. 

Exposed (as applied to wiring methods). On or attached 
to the surface or behind panels designed to allow access. 

Externally Operable. Capable of being operated without 
exposing the operator to contact with live parts. 

Feeder. All circuit conductors between the service equip- 
ment, the source of a separately derived system, or other 
power supply source and the final branch-circuit overcur- 
rent device. 

Festoon Lighting. A string of outdoor lights that is sus- 
pended between two points. 

Fitting. An accessory such as a locknut, bushing, or other 
part of a wiring system that is intended primarily to per- 
form a mechanical rather than an electrical function. 

Garage. A building or portion of a building in which one or 
more self-propelled vehicles can be kept for use, sale, stor- 
age, rental, repair, exhibition, or demonstration purposes. 

FPN: For commercial garages, repair and storage, see Ar- 
ticle 511. 

Ground. A conducting connection, whether intentional or 
accidental, between an electrical circuit or equipment and 
the earth or to some conducting body that serves in place of 
the earth. 

Grounded. Connected to earth or to some conducting body 
that serves in place of the earth. 

Grounded, Effectively. Intentionally connected to earth 
through a ground connection or connections of sufficiently 
low impedance and having sufficient current-carrying ca- 
pacity to prevent the buildup of voltages that may result in 
undue hazards to connected equipment or to persons. 

Grounded Conductor. A system or circuit conductor that 
is intentionally grounded. 

Grounding Conductor. A conductor used to connect 
equipment or the grounded circuit of a wiring system to a 
grounding electrode or electrodes. 

Grounding Conductor, Equipment. The conductor used 
to connect the non-current-carrying metal parts of equip- 
ment, raceways, and other enclosures to the system 
grounded conductor, the grounding electrode conductor, or 
both, at the service equipment or at the source of a sepa- 
rately derived system. 



NATIONAL ELECTRICAL CODE 



2002 Edition 



70-36 



ARTICLE 100 — DEFINITIONS 



Grounding Electrode Conductor. The conductor used to 
connect the grounding electrode(s) to the equipment 
grounding conductor, to the grounded conductor, or to both, 
at the service, at each building or structure where supplied 
from a common service, or at the source of a separately de- 
rived system. 

Ground-Fault Circuit Interrupter. A device intended for 
the protection of personnel that functions to de-energize a 
circuit or portion thereof within an established period of 
time when a current to ground exceeds the values estab- 
lished for a Class A device. 

FPN: Class A ground-fault circuit interrupters trip when 
the current to ground has a value in the range of 4 mA to 
6 mA. For further information, see UL 943, Standard for 
Ground-Fault Circuit Interrupters. 

Ground-Fault Protection of Equipment. A system in- 
tended to provide protection of equipment from damaging 
line-to-ground fault currents by operating to cause a discon- 
necting means to open all ungrounded conductors of the 
faulted circuit. This protection is provided at current levels 
less than those required to protect conductors from damage 
through the operation of a supply circuit overcurrent de- 
vice. 

Guarded. Covered, shielded, fenced, enclosed, or other- 
wise protected by means of suitable covers, casings, barri- 
ers, rails, screens, mats, or platforms to remove the likeli- 
hood of approach or contact by persons or objects to a point 
of danger. 

Hoistway. Any shaftway, hatchway, well hole, or other ver- 
tical opening or space in which an elevator or dumbwaiter 
is designed to operate. 

Identified (as applied to equipment). Recognizable as 
suitable for the specific purpose, function, use, environ- 
ment, application, and so forth, where described in a par- 
ticular Code requirement. 

FPN: Some examples of ways to determine suitability of 
equipment for a specific purpose, environment, or applica- 
tion include investigations by a qualified testing laboratory 
(listing and labeling), an inspection agency, or other orga- 
nizations concerned with product evaluation. 

In Sight From (Within Sight From, Within Sight). 

Where this Code specifies that one equipment shall be "in 
sight from," "within sight from," or "within sight," and so 
forth, of another equipment, the specified equipment is to 
be visible and not more than 15 m (50 ft) distant from the 
other. 

Interrupting Rating. The highest current at rated voltage 
that a device is intended to interrupt under standard test 
conditions. 

FPN: Equipment intended to interrupt current at other than 
fault levels may have its interrupting rating implied in other 
ratings, such as horsepower or locked rotor current. 



Isolated (as applied to location). Not readily accessible to 
persons unless special means for access are used. 

Labeled. Equipment or materials to which has been at- 
tached a label, symbol, or other identifying mark of an 
organization that is acceptable to the authority having juris- 
diction and concerned with product evaluation, that main- 
tains periodic inspection of production of labeled equip- 
ment or materials, and by whose labeling the manufacturer 
indicates compliance with appropriate standards or perfor- 
mance in a specified manner. 

Lighting Outlet. An outlet intended for the direct connec- 
tion of a lampholder, a luminaire (lighting fixture), or a 
pendant cord terminating in a lampholder. 

Listed. Equipment, materials, or services included in a list 
published by an organization that is acceptable to the au- 
thority having jurisdiction and concerned with evaluation 
of products or services, that maintains periodic inspection 
of production of listed equipment or materials or periodic 
evaluation of services, and whose listing states that the 
equipment, material, or services either meets appropriate 
designated standards or has been tested and found suitable 
for a specified purpose. 

FPN: The means for identifying listed equipment may vary 
for each organization concerned with product evaluation, 
some of which do not recognize equipment as listed unless 
it is also labeled. Use of the system employed by the listing 
organization allows the authority having jurisdiction to 
identify a listed product. 

Live Parts. Energized conductive components. 

Location, Damp. Locations protected from weather and 
not subject to saturation with water or other liquids but 
subject to moderate degrees of moisture. Examples of such 
locations include partially protected locations under cano- 
pies, marquees, roofed open porches, and like locations, 
and interior locations subject to moderate degrees of mois- 
ture, such as some basements, some barns, and some cold- 
storage warehouses. 

Location, Dry. A location not normally subject to damp- 
ness or wetness. A location classified as dry may be tem- 
porarily subject to dampness or wetness, as in the case of a 
building under construction. 

Location, Wet. Installations under ground or in concrete 
slabs or masonry in direct contact with the earth; in loca- 
tions subject to saturation with water or other liquids, such 
as vehicle washing areas; and in unprotected locations ex- 
posed to weather. 

Luminaire. A complete lighting unit consisting of a lamp 
or lamps together with the parts designed to distribute the 
light, to position and protect the lamps and ballast (where 
applicable), and to connect the lamps to the power supply. 



• 



2002 Edition 



NATIONAL ELECTRICAL CODE 



ARTICLE 100 — DEFINITIONS 



70-37 



Metal-Enclosed Power Switchgear. A switchgear assem- 
bly completely enclosed on all sides and top with sheet 
metal (except for ventilating openings and inspection win- 
dows) containing primary power circuit switching, inter- 
rupting devices, or both, with buses and connections. The 
assembly may include control and auxiliary devices. Access 
to the interior of the enclosure is provided by doors, remov- 
able covers, or both. 

Motor Control Center. An assembly of one or more en- 
closed sections having a common power bus and princi- 
pally containing motor control units. 

Multioutlet Assembly. A type of surface, flush, or free- 
standing raceway designed to hold conductors and recep- 
tacles, assembled in the field or at the factory. 

Nonautomatic. Action requiring personal intervention for 
its control. As applied to an electric controller, nonauto- 
matic control does not necessarily imply a manual control- 
ler, but only that personal intervention is necessary. 

Nonincendive Circuit. A circuit, other than field wiring, in 
which any arc or thermal effect produced under intended 
operating conditions of the equipment is not capable, under 
specified test conditions, of igniting the flammable gas-air, 
vapor-air, or dust-air mixture. 

FPN: For test conditions, see ANSI/ISA-SI 2. 12- 1994, 
Nonincendive Electrical Equipment for Use in Class I and 
II, Division 2 and Class III, Divisions 1 and 2 Hazardous 
(Classified) Locations. 

Nonincendive Field Wiring. Wiring that enters or leaves 
an equipment enclosure and, under normal operating con- 
ditions of the equipment, is not capable, due to arcing or 
thermal effects, of igniting the flammable gas-air, vapor- 
air, or dust-air mixture. Normal operation includes open- 
ing, shorting, or grounding the field wiring. 

Nonlinear Load. A load where the wave shape of the 
steady-state current does not follow the wave shape of the 
applied voltage. 

FPN: Electronic equipment, electronic/electric-discharge 
lighting, adjustable-speed drive systems, and similar equip- 
ment may be nonlinear loads. 

Outlet. A point on the wiring system at which current is 
taken to supply utilization equipment. 

Outline Lighting. An arrangement of incandescent lamps 
or electric-discharge lighting to outline or call attention to 
certain features such as the shape of a building or the deco- 
ration of a window. 

Overcurrent. Any current in excess of the rated current of 
equipment or the ampacity of a conductor. It may result 
from overload, short circuit, or ground fault. 



FPN: A current in excess of rating may be accommodated 
by certain equipment and conductors for a given set of 
conditions. Therefore the rules for overcurrent protection 
are specific for particular situations. 

Overload. Operation of equipment in excess of normal, 
full-load rating, or of a conductor in excess of rated ampac- 
ity that, when it persists for a sufficient length of time, 
would cause damage or dangerous overheating. A fault, 
such as a short circuit or ground fault, is not an overload. 

Panelboard. A single panel or group of panel units de- 
signed for assembly in the form of a single panel, including 
buses and automatic overcurrent devices, and equipped 
with or without switches for the control of light, heat, or 
power circuits; designed to be placed in a cabinet or cutout 
box placed in or against a wall, partition, or other support; 
and accessible only from the front. 

Plenum. A compartment or chamber to which one or more 
air ducts are connected and that forms part of the air distri- 
bution system. 

Power Outlet. An enclosed assembly that may include re- 
ceptacles, circuit breakers, fuseholders, fused switches, 
buses, and watt-hour meter mounting means; intended to 
supply and control power to mobile homes, recreational 
vehicles, park trailers, or boats or to serve as a means for 
distributing power required to operate mobile or tempo- 
rarily installed equipment. 

Premises Wiring (System). That interior and exterior wir- 
ing, including power, lighting, control, and signal circuit 
wiring together with all their associated hardware, fittings, 
and wiring devices, both permanently and temporarily in- 
stalled, that extends from the service point or source of 
power, such as a battery, a solar photovoltaic system, or a 
generator, transformer, or converter windings, to the out- 
lets). Such wiring does not include wiring internal to ap- 
pliances, luminaires (fixtures), motors, controllers, motor 
control centers, and similar equipment. 

Qualified Person. One who has skills and knowledge re- 
lated to the construction and operation of the electrical 
equipment and installations and has received safety training 
on the hazards involved. 

Raceway. An enclosed channel of metal or nonmetallic 
materials designed expressly for holding wires, cables, or 
busbars, with additional functions as permitted in this 
Code. Raceways include, but are not limited to, rigid metal 
conduit, rigid nonmetallic conduit, intermediate metal con- 
duit, liquidtight flexible conduit, flexible metallic tubing, 
flexible metal conduit, electrical nonmetallic tubing, elec- 
trical metallic tubing, underfloor raceways, cellular con- 
crete floor raceways, cellular metal floor raceways, surface 
raceways, wireways, and bus ways. 



NATIONAL ELECTRICAL CODE 



2002 Edition 



70-38 



ARTICLE 100 — DEFINITIONS 



Rainproof. Constructed, protected, or treated so as to pre- 
vent rain from interfering with the successful operation of 
the apparatus under specified test conditions. 

Raintight. Constructed or protected so that exposure to a 
beating rain will not result in the entrance of water under 
specified test conditions. 

Receptacle. A receptacle is a contact device installed at the 
outlet for the connection of an attachment plug. A single 
receptacle is a single contact device with no other contact 
device on the same yoke. A multiple receptacle is two or 
more contact devices on the same yoke. 

Receptacle Outlet. An outlet where one or more recep- 
tacles are installed. 

Remote-Control Circuit. Any electric circuit that controls 
any other circuit through a relay or an equivalent device. 

Sealable Equipment. Equipment enclosed in a case or 
cabinet that is provided with a means of sealing or locking 
so that live parts cannot be made accessible without open- 
ing the enclosure. The equipment may or may not be oper- 
able without opening the enclosure. 

Separately Derived System. A premises wiring system 
whose power is derived from a battery, from a solar photo- 
voltaic system, or from a generator, transformer, or con- 
verter windings, and that has no direct electrical connec- 
tion, including a solidly connected grounded circuit conductor, 
to supply conductors originating in another system. 

Service. The conductors and equipment for delivering elec- 
tric energy from the serving utility to the wiring system of 
the premises served. 

Service Cable. Service conductors made up in the form of 
a cable. 

Service Conductors. The conductors from the service 
point to the service disconnecting means. 

Service Drop. The overhead service conductors from the 
last pole or other aerial support to and including the splices, 
if any, connecting to the service-entrance conductors at the 
building or other structure. 

Service-Entrance Conductors, Overhead System. The 

service conductors between the terminals of the service 
equipment and a point usually outside the building, clear of 
building walls, where joined by tap or splice to the service 
drop. 

Service-Entrance Conductors, Underground System. 

The service conductors between the terminals of the service 
equipment and the point of connection to the service lateral. 

FPN: Where service equipment is located outside the 
building walls, there may be no service-entrance conduc- 
tors, or they may be entirely outside the building. 



Service Equipment. The necessary equipment, usually 
consisting of a circuit breaker(s) or switch(es) and fuse(s) 
and their accessories, connected to the load end of service 
conductors to a building or other structure, or an otherwise 
designated area, and intended to constitute the main control 
and cutoff of the supply. 

Service Lateral. The underground service conductors be- 
tween the street main, including any risers at a pole or other 
structure or from transformers, and the first point of con- 
nection to the service-entrance conductors in a terminal box 
or meter or other enclosure, inside or outside the building 
wall. Where there is no terminal box, meter, or other enclo- 
sure, the point of connection is considered to be the point of 
entrance of the service conductors into the building. 

Service Point. The point of connection between the facili- 
ties of the serving utility and the premises wiring. 

Show Window. Any window used or designed to be used 
for the display of goods or advertising material, whether it 
is fully or partly enclosed or entirely open at the rear and 
whether or not it has a platform raised higher than the street 
floor level. 

Signaling Circuit. Any electric circuit that energizes sig- 
naling equipment. 

Solar Photovoltaic System. The total components and sub- 
systems that, in combination, convert solar energy into 
electrical energy suitable for connection to a utilization 
load. 

Special Permission. The written consent of the authority 
having jurisdiction. 

Structure. That which is built or constructed. 

Switch, Bypass Isolation. A manually operated device 
used in conjunction with a transfer switch to provide a 
means of directly connecting load conductors to a power 
source and of disconnecting the transfer switch. 

Switch, General-Use. A switch intended for use in general 
distribution and branch circuits. It is rated in amperes, and 
it is capable of interrupting its rated current at its rated 
voltage. 

Switch, General-Use Snap. A form of general-use switch 
constructed so that it can be installed in device boxes or on 
box covers, or otherwise used in conjunction with wiring 
systems recognized by this Code. 

Switch, Isolating. A switch intended for isolating an elec- 
tric circuit from the source of power. It has no interrupting 
rating, and it is intended to be operated only after the circuit 
has been opened by some other means. 

Switch, Motor-Circuit. A switch rated in horsepower that 
is capable of interrupting the maximum operating overload 



2002 Edition 



NATIONAL ELECTRICAL CODE 



ARTICLE 100 — DEFINITIONS 



70-39 



current of a motor of the same horsepower rating as the 
switch at the rated voltage. 

Switch, Transfer. An automatic or nonautomatic device for 
transferring one or more load conductor connections from 
one power source to another. 

Switchboard. A large single panel, frame, or assembly of 
panels on which are mounted on the face, back, or both, 
switches, overcurrent and other protective devices, buses, 
and usually instruments. Switchboards are generally acces- 
sible from the rear as well as from the front and are not 
intended to be installed in cabinets. 

Thermal Protector (as applied to motors). A protective 
device for assembly as an integral part of a motor or motor- 
compressor that, when properly applied, protects the motor 
against dangerous overheating due to overload and failure 
to start. 

FPN: The thermal protector may consist of one or more 
sensing elements integral with the motor or motor- 
compressor and an external control device. 

Thermally Protected (as applied to motors). The words 
Thermally Protected appearing on the nameplate of a motor 
or motor-compressor indicate that the motor is provided 
with a thermal protector. 

Utilization Equipment. Equipment that utilizes electric 
energy for electronic, electromechanical, chemical, heating, 
lighting, or similar purposes. 

Ventilated. Provided with a means to permit circulation of 
air sufficient to remove an excess of heat, fumes, or vapors. 

Volatile Flammable Liquid. A flammable liquid having a 
flash point below 38°C (100°F), or a flammable liquid 
whose temperature is above its flash point, or a Class II 
combustible liquid that has a vapor pressure not exceeding 
276 kPa (40 psia) at 38°C (100°F) and whose temperature 
is above its flash point. 

Voltage (of a circuit). The greatest root-mean-square (rms) 
(effective) difference of potential between any two conduc- 
tors of the circuit concerned. 

FPN: Some systems, such as 3-phase 4-wire, single-phase 
3-wire, and 3-wire direct current, may have various circuits 
of various voltages. 

Voltage, Nominal. A nominal value assigned to a circuit or 
system for the purpose of conveniently designating its volt- 
age class (e.g., 120/240 volts, 480Y/277 volts, 600 volts). 
The actual voltage at which a circuit operates can vary 
from the nominal within a range that permits satisfactory 
operation of equipment. 

FPN: See ANSI C84. 1-1995, Voltage Ratings for Electric 
Power Systems and Equipment (60 Hz). 



Voltage to Ground. For grounded circuits, the voltage be- 
tween the given conductor and that point or conductor of 
the circuit that is grounded; for ungrounded circuits, the 
greatest voltage between the given conductor and any other 
conductor of the circuit. 

Watertight. Constructed so that moisture will not enter the 
enclosure under specified test conditions. 

Weatherproof. Constructed or protected so that exposure 
to the weather will not interfere with successful operation. 

FPN: Rainproof, raintight, or watertight equipment can ful- 
fill the requirements for weatherproof where varying 
weather conditions other than wetness, such as snow, ice, 
dust, or temperature extremes, are not a factor. 

II. Over 600 Volts, Nominal 

Whereas the preceding definitions are intended to apply 
wherever the terms are used throughout this Code, the fol- 
lowing definitions are applicable only to parts of the article 
specifically covering installations and equipment operating 
at over 600 volts, nominal. 

Electronically Actuated Fuse. An overcurrent protective 
device that generally consists of a control module that pro- 
vides current sensing, electronically derived time-current 
characteristics, energy to initiate tripping, and an interrupt- 
ing module that interrupts current when an overcurrent oc- 
curs. Electronically actuated fuses may or may not operate 
in a current-limiting fashion, depending on the type of con- 
trol selected. 

Fuse. An overcurrent protective device with a circuit- 
opening fusible part that is heated and severed by the pas- 
sage of overcurrent through it. 

FPN: A fuse comprises all the parts that form a unit ca- 
pable of performing the prescribed functions. It may or may 
not be the complete device necessary to connect it into an 
electrical circuit. 

Controlled Vented Power Fuse. A fuse with provision for 
controlling discharge circuit interruption such that no solid 
material may be exhausted into the surrounding atmo- 
sphere. 

FPN: The fuse is designed so that discharged gases will not 
ignite or damage insulation in the path of the discharge or 
propagate a flashover to or between grounded members or 
conduction members in the path of the discharge where the 
distance between the vent and such insulation or conduc- 
tion members conforms to manufacturer's recommenda- 
tions. 

Expulsion Fuse Unit (Expulsion Fuse). A vented fuse unit 
in which the expulsion effect of gases produced by the arc 
and lining of the fuseholder, either alone or aided by a 
spring, extinguishes the arc. 



NATIONAL ELECTRICAL CODE 



2002 Edition 



70-40 



ARTICLE 110 — REQUIREMENTS FOR ELECTRICAL INSTALLATIONS 



Nonvented Power Fuse. A fuse without intentional provi- 
sion for the escape of arc gases, liquids, or solid particles to 
the atmosphere during circuit interruption. 
Power Fuse Unit. A vented, nonvented, or controlled 
vented fuse unit in which the arc is extinguished by being 
drawn through solid material, granular material, or liquid, 
either alone or aided by a spring. 

Vented Power Fuse. A fuse with provision for the escape of 
arc gases, liquids, or solid particles to the surrounding at- 
mosphere during circuit interruption. 

Multiple Fuse. An assembly of two or more single-pole 
fuses. 

Switching Device. A device designed to close, open, or 
both, one or more electric circuits. 

Circuit Breaker. A switching device capable of making, 
carrying, and interrupting currents under normal circuit 
conditions, and also of making, carrying for a specified 
time, and interrupting currents under specified abnormal 
circuit conditions, such as those of short circuit. 
Cutout. An assembly of a fuse support with either a fuse- 
holder, fuse carrier, or disconnecting blade. The fuseholder 
or fuse carrier may include a conducting element (fuse link) 
or may act as the disconnecting blade by the inclusion of a 
nonfusible member. 

Disconnecting (or Isolating) Switch (Disconnector, Isola- 
tor). A mechanical switching device used for isolating a 
circuit or equipment from a source of power. 
Disconnecting Means. A device, group of devices, or other 
means whereby the conductors of a circuit can be discon- 
nected from their source of supply. 

Interrupter Switch. A switch capable of making, carrying, 
and interrupting specified currents. 

Oil Cutout (Oil-Filled Cutout). A cutout in which all or 
part of the fuse support and its fuse link or disconnecting 
blade is mounted in oil with complete immersion of the 
contacts and the fusible portion of the conducting element 
(fuse link) so that arc interruption by severing of the fuse 
link or by opening of the contacts will occur under oil. 
Oil Switch. A switch having contacts that operate under oil 
(or askarel or other suitable liquid). 

Regulator Bypass Switch. A specific device or combination 
of devices designed to bypass a regulator. 



to and spaces about electrical conductors and equipment, 
and tunnel installations. 

110.2 Approval. The conductors and equipment required 
or permitted by this Code shall be acceptable only if ap- 
proved. 

FPN: See 90.7, Examination of Equipment for Safety, and 
110.3, Examination, Identification, Installation, and Use of 
Equipment. See definitions of Approved, Identified, La- 
beled, and Listed. 

110.3 Examination, Identification, Installation, and Use 
of Equipment. 

(A) Examination. In judging equipment, considerations 
such as the following shall be evaluated: 

(1) Suitability for installation and use in conformity with 
the provisions of this Code 

FPN: Suitability of equipment use may be identified by a 
description marked on or provided with a product to iden- 
tify the suitability of the product for a specific purpose, 
environment, or application. Suitability of equipment may 
be evidenced by listing or labeling. 

(2) Mechanical strength and durability, including, for parts 
designed to enclose and protect other equipment, the 
adequacy of the protection thus provided 

(3) Wire -bending and connection space 

(4) Electrical insulation 

(5) Heating effects under normal conditions of use and also 
under abnormal conditions likely to arise in service 

(6) Arcing effects 

(7) Classification by type, size, voltage, current capacity, 
and specific use 

(8) Other factors that contribute to the practical safeguard- 
ing of persons using or likely to come in contact with 
the equipment 

(B) Installation and Use. Listed or labeled equipment 
shall be installed and used in accordance with any instruc- 
tions included in the listing or labeling. 

110.4 Voltages. Throughout this Code, the voltage consid- 
ered shall be that at which the circuit operates. The voltage 
rating of electrical equipment shall not be less than the 
nominal voltage of a circuit to which it is connected. 



ARTICLE 110 
Requirements for Electrical Installations 



I. General 

110.1 Scope. This article covers general requirements for 
the examination and approval, installation and use, access 



110.5 Conductors. Conductors normally used to carry cur- 
rent shall be of copper unless otherwise provided in this 
Code. Where the conductor material is not specified, the 
material and the sizes given in this Code shall apply to 
copper conductors. Where other materials are used, the size 
shall be changed accordingly. 

FPN: For aluminum and copper-clad aluminum conduc- 
tors, see 310.15. 



2002 Edition 



NATIONAL ELECTRICAL CODE 



ARTICLE 110 — REQUIREMENTS FOR ELECTRICAL INSTALLATIONS 



70-41 



• 



110.6 Conductor Sizes. Conductor sizes are expressed in 
American Wire Gage (AWG) or in circular mils. 

110.7 Insulation Integrity. Completed wiring installations 
shall be free from short circuits and from grounds other 
than as required or permitted in Article 250. 

110.8 Wiring Methods. Only wiring methods recognized 
as suitable are included in this Code. The recognized meth- 
ods of wiring shall be permitted to be installed in any type 
of building or occupancy, except as otherwise provided in 
this Code. 

110.9 Interrupting Rating. Equipment intended to inter- 
rupt current at fault levels shall have an interrupting rating 
sufficient for the nominal circuit voltage and the current 
that is available at the line terminals of the equipment. 

Equipment intended to interrupt current at other than 
fault levels shall have an interrupting rating at nominal 
circuit voltage sufficient for the current that must be inter- 
rupted. 

110.10 Circuit Impedance and Other Characteristics. 

The overcurrent protective devices, the total impedance, the 
component short-circuit current ratings, and other charac- 
teristics of the circuit to be protected shall be selected and 
coordinated to permit the circuit-protective devices used to 
clear a fault to do so without extensive damage to the elec- 
trical components of the circuit. This fault shall be assumed 
to be either between two or more of the circuit conductors 
or between any circuit conductor and the grounding con- 
ductor or enclosing metal raceway. Listed products applied 
in accordance with their listing shall be considered to meet 
the requirements of this section. 

110.11 Deteriorating Agents. Unless identified for use in 
the operating environment, no conductors or equipment 
shall be located in damp or wet locations; where exposed to 
gases, fumes, vapors, liquids, or other agents that have a 
deteriorating effect on the conductors or equipment; or 
where exposed to excessive temperatures. 

FPN No. 1 : See 300.6 for protection against corrosion. 

FPN No. 2: Some cleaning and lubricating compounds can 
cause severe deterioration of many plastic materials used 
for insulating and structural applications in equipment. 

Equipment identified only as "dry locations," "Type 1," 
or "indoor use only" shall be protected against permanent 
damage from the weather during building construction. 

110.12 Mechanical Execution of Work. Electrical equip- 
ment shall be installed in a neat and workmanlike manner. 



(A) Unused Openings. Unused cable or raceway openings 
in boxes, raceways, auxiliary gutters, cabinets, cutout 
boxes, meter socket enclosures, equipment cases, or hous- 
ings shall be effectively closed to afford protection substan- 
tially equivalent to the wall of the equipment. Where me- 
tallic plugs or plates are used with nonmetallic enclosures, 
they shall be recessed at least 6 mm i}U in.) from the outer 
surface of the enclosure. 

(B) Subsurface Enclosures. Conductors shall be racked to 
provide ready and safe access in underground and subsur- 
face enclosures into which persons enter for installation and 
maintenance. 

(C) Integrity of Electrical Equipment and Connections. 

Internal parts of electrical equipment, including busbars, 
wiring terminals, insulators, and other surfaces, shall not be 
damaged or contaminated by foreign materials such as 
paint, plaster, cleaners, abrasives, or corrosive residues. 
There shall be no damaged parts that may adversely affect 
safe operation or mechanical strength of the equipment 
such as parts that are broken; bent; cut; or deteriorated by 
corrosion, chemical action, or overheating. 

110.13 Mounting and Cooling of Equipment. 

(A) Mounting. Electrical equipment shall be firmly se- 
cured to the surface on which it is mounted. Wooden plugs 
driven into holes in masonry, concrete, plaster, or similar 
materials shall not be used. 

(B) Cooling. Electrical equipment that depends on the 
natural circulation of air and convection principles for cool- 
ing of exposed surfaces shall be installed so that room 
airflow over such surfaces is not prevented by walls or by 
adjacent installed equipment. For equipment designed for 
floor mounting, clearance between top surfaces and adja- 
cent surfaces shall be provided to dissipate rising warm air. 

Electrical equipment provided with ventilating open- 
ings shall be installed so that walls or other obstructions do 
not prevent the free circulation of air through the equip- 
ment. 

110.14 Electrical Connections. Because of different char- 
acteristics of dissimilar metals, devices such as pressure 
terminal or pressure splicing connectors and soldering lugs 
shall be identified for the material of the conductor and 
shall be properly installed and used. Conductors of dissimi- 
lar metals shall not be intermixed in a terminal or splicing 
connector where physical contact occurs between dissimilar 
conductors (such as copper and aluminum, copper and 
copper-clad aluminum, or aluminum and copper-clad alu- 
minum), unless the device is identified for the purpose and 
conditions of use. Materials such as solder, fluxes, inhibi- 
tors, and compounds, where employed, shall be suitable for 



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the use and shall be of a type that will not adversely affect 
the conductors, installation, or equipment. 

FPN: Many terminations and equipment are marked with a 
tightening torque. 

(A) Terminals. Connection of conductors to terminal parts 
shall ensure a thoroughly good connection without damag- 
ing the conductors and shall be made by means of pressure 
connectors (including set-screw type), solder lugs, or 
splices to flexible leads. Connection by means of wire- 
binding screws or studs and nuts that have upturned lugs or 
the equivalent shall be permitted for 10 AWG or smaller 
conductors. 

Terminals for more than one conductor and terminals 
used to connect aluminum shall be so identified. 

(B) Splices. Conductors shall be spliced or joined with 
splicing devices identified for the use or by brazing, weld- 
ing, or soldering with a fusible metal or alloy. Soldered 
splices shall first be spliced or joined so as to be mechani- 
cally and electrically secure without solder and then be 
soldered. All splices and joints and the free ends of conduc- 
tors shall be covered with an insulation equivalent to that of 
the conductors or with an insulating device identified for 
the purpose. 

Wire connectors or splicing means installed on conduc- 
tors for direct burial shall be listed for such use. 

(C) Temperature Limitations. The temperature rating as- 
sociated with the ampacity of a conductor shall be selected 
and coordinated so as not to exceed the lowest temperature 
rating of any connected termination, conductor, or device. 
Conductors with temperature ratings higher than specified 
for terminations shall be permitted to be used for ampacity 
adjustment, correction, or both. 

(1) Equipment Provisions. The determination of termina- 
tion provisions of equipment shall be based on 
110.14(C)(1)(a) or (C)(1)(b). Unless the equipment is listed 
and marked otherwise, conductor ampacities used in deter- 
mining equipment termination provisions shall be based on 
Table 310.16 as appropriately modified by 310.15(B)(1) 
through (6). 

(a) Termination provisions of equipment for circuits 
rated 100 amperes or less, or marked for 14 AWG through 
1 AWG conductors, shall be used only for one of the follow- 
ing: 

(1) Conductors rated 60°C (140°F) 

(2) Conductors with higher temperature ratings, provided 
the ampacity of such conductors is determined based 
on the 60°C (140°F) ampacity of the conductor size 
used 

(3) Conductors with higher temperature ratings if the 
equipment is listed and identified for use with such 
conductors 



(4) For motors marked with design letters B, C, D, or E, 
conductors having an insulation rating of 75°C (167°F) 
or higher shall be permitted to be used provided the 
ampacity of such conductors does not exceed the 75°C 
(167°F) ampacity. 

(b) Termination provisions of equipment for circuits 
rated over 100 amperes, or marked for conductors larger 
than 1 AWG, shall be used only for one of the following: 

(1) Conductors rated 75°C (167°F) 

(2) Conductors with higher temperature ratings, provided 
the ampacity of such conductors does not exceed the 
75°C (167°F) ampacity of the conductor size used, or 
up to their ampacity if the equipment is listed and iden- 
tified for use with such conductors 

(2) Separate Connector Provisions. Separately installed 
pressure connectors shall be used with conductors at the 
ampacities not exceeding the ampacity at the listed and 
identified temperature rating of the connector. 

FPN: With respect to 110.14(C)(1) and (2), equipment 
markings or listing information may additionally restrict 
the sizing and temperature ratings of connected conductors. 

110.15 High-Leg Marking. On a 4-wire, delta-connected 
system where the midpoint of one phase winding is 
grounded to supply lighting and similar loads, the conduc- 
tor or busbar having the higher phase voltage to ground 
shall be durably and permanently marked by an outer finish 
that is orange in color or by other effective means. Such 
identification shall be placed at each point on the system 
where a connection is made if the grounded conductor is 
also present. 

110.16 Flash Protection. Switchboards, panelboards, in- 
dustrial control panels, and motor control centers that are in 
other than dwelling occupancies and are likely to require 
examination, adjustment, servicing, or maintenance while 
energized shall be field marked to warn qualified persons of 
potential electric arc flash hazards. The marking shall be 
located so as to be clearly visible to qualified persons be- 
fore examination, adjustment, servicing, or maintenance of 
the equipment. 

FPN No. 1: NFPA 70E-2000, Electrical Safety Require- 
ments for Employee Workplaces, provides assistance in de- 
termining severity of potential exposure, planning safe 
work practices, and selecting personal protective 
equipment. 

FPN No. 2: ANSI Z535.4-1998, Product Safety Signs and 
Labels, provides guidelines for the design of safety signs 
and labels for application to products. 

110.18 Arcing Parts. Parts of electric equipment that in 
ordinary operation produce arcs, sparks, flames, or molten 
metal shall be enclosed or separated and isolated from all 
combustible material. 



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70-43 



• 



FPN: For hazardous (classified) locations, see Articles 500 
through 517. For motors, see 430.14. 

110.19 Light and Power from Railway Conductors. 

Circuits for lighting and power shall not be connected to 
any system that contains trolley wires with a ground return.. 

Exception: Such circuit connections shall be permitted in 
car houses, power houses, or passenger and freight stations 
operated in connection with electric railways. 

110.21 Marking. The manufacturer's name, trademark, or 
other descriptive marking by which the organization re- 
sponsible for the product can be identified shall be placed 
on all electric equipment. Other markings that indicate volt- 
age, current, wattage, or other ratings shall be provided as 
specified elsewhere in this Code. The marking shall be of 
sufficient durability to withstand the environment involved. 

110.22 Identification of Disconnecting Means. Each dis- 
connecting means shall be legibly marked to indicate its 
purpose unless located and arranged so the purpose is evi- 
dent. The marking shall be of sufficient durability to with- 
stand the environment involved. 

Where circuit breakers or fuses are applied in compli- 
ance with the series combination ratings marked on the 
equipment by the manufacturer, the equipment enclosure(s) 
shall be legibly marked in the field to indicate the equip- 
ment has been applied with a series combination rating. 
The marking shall be readily visible and state the following: 

CAUTION — SERIES COMBINATION SYSTEM 

RATED AMPERES. IDENTIFIED 

REPLACEMENT COMPONENTS REQUIRED. 

FPN: See Section 240.86(A) for interrupting rating mark- 
ing for end-use equipment. 

110.23 Current Transformers. Unused current transform- 
ers associated with potentially energized circuits shall be 
short-circuited. 



II. 600 Volts, Nominal, or Less 

110.26 Spaces About Electrical Equipment. Sufficient 
access and working space shall be provided and maintained 
about all electric equipment to permit ready and safe opera- 
tion and maintenance of such equipment. Enclosures hous- 
ing electrical apparatus that are controlled by lock and key 
shall be considered accessible to qualified persons. 

(A) Working Space. Working space for equipment operat- 
ing at 600 volts, nominal, or less to ground and likely to 
require examination, adjustment, servicing, or maintenance 
while energized shall comply with the dimensions of 



110.26(A)(1), (2), and (3) or as required or permitted else- 
where in this Code. 

(1) Depth of Working Space. The depth of the working 
space in the direction of live parts shall not be less than that 
specified in Table 110.26(A)(1) unless the requirements of 
110.26(A)(1)(a), (b), or (c) are met. Distances shall be mea- 
sured from the exposed live parts or from the enclosure or 
opening if the live parts are enclosed. 

Table 110.26(A)(1) Working Spaces 



Nominal 
Voltage to ■ 
Ground 


Minimum Clear Distance 


Condition 1 Condition 2 Condition 3 


0-150 
151-600 


900 mm (3 ft) 900 mm (3 ft) 900 mm (3 ft) 
900 mm (3 ft) 1 m {Vh ft) 1.2 m (4 ft) 



Note: Where the conditions are as follows: 

Condition 1 — Exposed live parts on one side and no live or 

grounded parts on the other side of the working space, or exposed live 

parts on both sides effectively guarded by suitable wood or other 

insulating materials. Insulated wire or insulated busbars operating at 

not over 300 volts to ground shall not be considered live parts. 

Condition 2 — Exposed live parts on one side and grounded parts on 

the other side. Concrete, brick, or tile walls shall be considered as 

grounded. 

Condition 3 — Exposed live parts on both sides of the work space 

(not guarded as provided in Condition 1) with the operator between. 



(a) Dead-Front Assemblies. Working space shall not 
be required in the back or sides of assemblies, such as 
dead-front switchboards or motor control centers, where all 
connections and all renewable or adjustable parts, such as 
fuses or switches, are accessible from locations other than 
the back or sides. Where rear access is required to work on 
nonelectrical parts on the back of enclosed equipment, a 
minimum horizontal working space of 762 mm (30 in.) 
shall be provided. 

(b) Low Voltage. By special permission, smaller work- 
ing spaces shall be permitted where all uninsulated parts 
operate at not greater than 30 volts rms, 42 volts peak, or 
60 volts dc. 

(c) Existing Buildings. In existing buildings where 
electrical equipment is being replaced, Condition 2 working 
clearance shall be permitted between dead-front switch- 
boards, panelboards, or motor control centers located 
across the aisle from each other where conditions of main- 
tenance and supervision ensure that written procedures 
have been adopted to prohibit equipment on both sides of 
the aisle from being open at the same time and qualified 
persons who are authorized will service the installation. 

(2) Width of Working Space. The width of the working 
space in front of the electric equipment shall be the width 
of the equipment or 750 mm (30 in.), whichever is greater. 



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In all cases, the work space shall permit at least a 90 degree 
opening of equipment doors or hinged panels. 

(3) Height of Working Space. The work space shall be 
clear and extend from the grade, floor, or platform to the 
height required by 110.26(E). Within the height require- 
ments of this section, other equipment that is associated 
with the electrical installation and is located above or be- 
low the electrical equipment shall be permitted to extend 
not more than 150 mm (6 in.) beyond the front of the 
electrical equipment. 

(B) Clear Spaces. Working space required by this section 
shall not be used for storage. When normally enclosed live 
parts are exposed for inspection or servicing, the working 
space, if in a passageway or general open space, shall be 
suitably guarded. 

(C) Entrance to Working Space. 

(1) Minimum Required. At least one entrance of suffi- 
cient area shall be provided to give access to working space 
about electrical equipment. 

(2) Large Equipment. For equipment rated 1200 amperes 
or more and over 1.8 m (6 ft) wide that contains overcur- 
rent devices, switching devices, or control devices, there 
shall be one entrance to the required working space not less 
than 610 mm (24 in.) wide and 2.0 m (6V2 ft) high at each 
end of the working space. Where the entrance has a person- 
nel door(s), the door(s) shall open in the direction of egress 
and be equipped with panic bars, pressure plates, or other 
devices that are normally latched but open under simple 
pressure. 

A single entrance to the required working space shall be 
permitted where either of the conditions in 110.26(C)(2)(a) 
or (b) is met. 

(a) Unobstructed Exit. Where the location permits a 
continuous and unobstructed way of exit travel, a single 
entrance to the working space shall be permitted. 

(b) Extra Working Space. Where the depth of the 
working space is twice that required by 110.26(A)(1), a 
single entrance shall be permitted. It shall be located so that 
the distance from the equipment to the nearest edge of the 
entrance is not less than the minimum clear distance speci- 
fied in Table 110.26(A)(1) for equipment operating at that 
voltage and in that condition. 

(D) Illumination. Illumination shall be provided for all 
working spaces about service equipment, switchboards, 
panelboards, or motor control centers installed indoors. Ad- 
ditional lighting outlets shall not be required where the 
work space is illuminated by an adjacent light source or as 
permitted by 210.70(A)(1), Exception No. 1, for switched 
receptacles. In electrical equipment rooms, the illumination 
shall not be controlled by automatic means only. 



(E) Headroom. The minimum headroom of working 
spaces about service equipment, switchboards, panelboards, 
or motor control centers shall be 2.0 m (6V2 ft). Where the 
electrical equipment exceeds 2.0 m (6V2 ft) in height, 
the minimum headroom shall not be less than the height of 
the equipment. 

Exception: In existing dwelling units, service equipment 
or panelboards that do not exceed 200 amperes shall be 
permitted in spaces where the headroom is less than 2.0 m 
(6^ ft). 

(F) Dedicated Equipment Space. All switchboards, pan- 
elboards, distribution boards, and motor control centers 
shall be located in dedicated spaces and protected from 
damage. 

Exception: Control equipment that by its very nature or 
because of other rules of the Code must be adjacent to or 
within sight of its operating machinery shall be permitted 
in those locations. 

(1) Indoor. Indoor installations shall comply with 
110.26(F)(1)(a) through (d). 

(a) Dedicated Electrical Space. The space equal to the 
width and depth of the equipment and extending from the 
floor to a height of 1.8 m (6 ft) above the equipment or to 
the structural ceiling, whichever is lower, shall be dedicated 
to the electrical installation. No piping, ducts, leak protec- 
tion apparatus, or other equipment foreign to the electrical 
installation shall be located in this zone. 

Exception: Suspended ceilings with removable panels shall 
be permitted within the 1.8-m (6-ft) zone. 

(b) Foreign Systems. The area above the dedicated 
space required by 110.26(F)(1)(a) shall be permitted to con- 
tain foreign systems, provided protection is installed to 
avoid damage to the electrical equipment from condensa- 
tion, leaks, or breaks in such foreign systems. 

(c) Sprinkler Protection. Sprinkler protection shall be 
permitted for the dedicated space where the piping com- 
plies with this section. 

(d) Suspended Ceilings. A dropped, suspended, or 
similar ceiling that does not add strength to the building 
structure shall not be considered a structural ceiling. 

(2) Outdoor. Outdoor electrical equipment shall be in- 
stalled in suitable enclosures and shall be protected from 
accidental contact by unauthorized personnel, or by vehicu- 
lar traffic, or by accidental spillage or leakage from piping 
systems. The working clearance space shall include the 
zone described in 110.26(A). No architectural appurtenance 
or other equipment shall be located in this zone. 

110.27 Guarding of Live Parts. 

(A) Live Parts Guarded Against Accidental Contact. 

Except as elsewhere required or permitted by this Code, 



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70-45 



live parts of electrical equipment operating at 50 volts or 
more shall be guarded against accidental contact by ap- 
proved enclosures or by any of the following means: 

(1) By location in a room, vault, or similar enclosure that is 
accessible only to qualified persons. 

(2) By suitable permanent, substantial partitions or screens 
arranged so that only qualified persons have access to 
the space within reach of the live parts. Any openings 
in such partitions or screens shall be sized and located 
so that persons are not likely to come into accidental 
contact with the live parts or to bring conducting ob- 
jects into contact with them. 

(3) By location on a suitable balcony, gallery, or platform 
elevated and arranged so as to exclude unqualified per- 
sons. 

(4) By elevation of 2.5 m (8 ft) or more above the floor or 
other working surface. 

(B) Prevent Physical Damage. In locations where electric 
equipment is likely to be exposed to physical damage, en- 
closures or guards shall be so arranged and of such strength 
as to prevent such damage. 

(C) Warning Signs. Entrances to rooms and other guarded 
locations that contain exposed live parts shall be marked 
with conspicuous warning signs forbidding unqualified per- 
sons to enter. 

FPN: For motors, see 430.132 and 430.133. For over 600 
volts, see 110.34. 

III. Over 600 Volts, Nominal 

110.30 General. Conductors and equipment used on cir- 
cuits over 600 volts, nominal, shall comply with Part I of 
this article and with the following sections, which supple- 
ment or modify Part I. In no case shall the provisions of 
this part apply to equipment on the supply side of the ser- 
vice point. 

110.31 Enclosure for Electrical Installations. Electrical 
installations in a vault, room, or closet or in an area sur- 
rounded by a wall, screen, or fence, access to which is 
controlled by lock and key or other approved means, shall 
be considered to be accessible to qualified persons only. 
The type of enclosure used in a given case shall be de- 
signed and constructed according to the nature and degree 
of the hazard(s) associated with the installation. 

For installations other than equipment as described in 
110.31(D), a wall, screen, or fence shall be used to enclose 
an outdoor electrical installation to deter access by persons 
who are not qualified. A fence shall not be less than 2. 1 m 
(7 ft) in height or a combination of 1.8 m (6 ft) or more of 
fence fabric and a 300-mm ( 1 -ft) or more extension utiliz- 
ing three or more strands of barbed wire or equivalent. The 



distance from the fence to live parts shall be not less than 
given in Table 110.31. 

Table 110.31 Minimum Distance from Fence to Live Parts 





Minimum Distance to 
Live Parts 


Nominal Voltage 


m ft 


601-13,799 
13,800-230,000 
Over 230,000 


3.05 10 
4.57 15 
5.49 18 



Note: For clearances of conductors for specific system voltages and 
typical BIL ratings, see ANSI C2-1997, National Electrical Safety 
Code. 



FPN: See Article 450 for construction requirements for 
transformer vaults. 

(A) Fire Resistivity of Electrical Vaults. The walls, roof, 
floors, and doorways of vaults containing conductors and 
equipment over 600 volts, nominal, shall be constructed of 
materials that have adequate structural strength for the con- 
ditions, with a minimum fire rating of 3 hours. The floors of 
vaults in contact with the earth shall be of concrete that is 
not less than 4 in. (102 mm) thick, but where the vault is 
constructed with a vacant space or other stories below it, 
the floor shall have adequate structural strength for the load 
imposed on it and a minimum fire resistance of 3 hours. For 
the purpose of this section, studs and wallboards shall not 
be considered acceptable. 

(B) Indoor Installations. 

(1) In Places Accessible to Unqualified Persons. Indoor 
electrical installations that are accessible to unqualified per- 
sons shall be made with metal-enclosed equipment. Metal- 
enclosed switchgear, unit substations, transformers, pull 
boxes, connection boxes, and other similar associated 
equipment shall be marked with appropriate caution signs. 
Openings in ventilated dry-type transformers or similar 
openings in other equipment shall be designed so that for- 
eign objects inserted through these openings are deflected 
from energized parts. 

(2) In Places Accessible to Qualified Persons Only. 

Indoor electrical installations considered accessible only to 
qualified persons in accordance with this section shall com- 
ply with 110.34, 110.36, and 490.24. 

(C) Outdoor Installations. 

(1) In Places Accessible to Unqualified Persons. Outdoor 
electrical installations that are open to unqualified persons 
shall comply with Article 225. 



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ARTICLE 110 — REQUIREMENTS FOR ELECTRICAL INSTALLATIONS 



FPN: For clearances of conductors for system voltages 
over 600 volts, nominal, see ANSI C2-1997, National Elec- 
trical Safety Code. 

(2) In Places Accessible to Qualified Persons Only. 

Outdoor electrical installations that have exposed live parts 
shall be accessible to qualified persons only in accordance 
with the first paragraph of this section and shall comply 
with 110.34, 110.36, and 490.24. 

(D) Enclosed Equipment Accessible to Unqualified 
Persons. Ventilating or similar openings in equipment shall 
be designed so that foreign objects inserted through these 
openings are deflected from energized parts. Where ex- 
posed to physical damage from vehicular traffic, suitable 
guards shall be provided. Nonmetallic or metal-enclosed 
equipment located outdoors and accessible to the general 
public shall be designed so that exposed nuts or bolts can- 
not be readily removed, permitting access to live parts. 
Where nonmetallic or metal-enclosed equipment is acces- 
sible to the general public and the bottom of the enclosure 
is less than 2.5 m (8 ft) above the floor or grade level, the 
enclosure door or hinged cover shall be kept locked. Doors 
and covers of enclosures used solely as pull boxes, splice 
boxes, or junction boxes shall be locked, bolted, or screwed 
on. Underground box covers that weigh over 45.4 kg 
(100 lb) shall be considered as meeting this requirement. 

110.32 Work Space About Equipment. Sufficient space 
shall be provided and maintained about electric equipment 
to permit ready and safe operation and maintenance of such 
equipment. Where energized parts are exposed, the mini- 
mum clear work space shall not be less than 2.0 m (6 L /2 ft) 
high (measured vertically from the floor or platform) or less 
than 900 mm (3 ft) wide (measured parallel to the equip- 
ment). The depth shall be as required in 110.34(A). In all 
cases, the work space shall permit at least a 90 degree 
opening of doors or hinged panels. 

110.33 Entrance and Access to Work Space. 

(A) Entrance. At least one entrance not less than 610 mm 
(24 in.) wide and 2.0 m (6V2 ft) high shall be provided to 
give access to the working space about electric equipment. 
Where the entrance has a personnel door(s), the door(s) 
shall open in the direction of egress and be equipped with 
panic bars, pressure plates, or other devices that are nor- 
mally latched but open under simple pressure. 

(1) Large Equipment. On switchboard and control panels 
exceeding 1.8 m (6 ft) in width, there shall be one entrance 
at each end of the equipment. A single entrance to the 
required working space shall be permitted where either of 
the conditions in 110.33(A)(1)(a) or (b) is met. 

(a) Unobstructed Exit. Where the location permits a 
continuous and unobstructed way of exit travel, a single 
entrance to the working space shall be permitted. 



(b) Extra Working Space. Where the depth of the 
working space is twice that required by 110.34(A), a single 
entrance shall be permitted. It shall be located so that the 
distance from the equipment to the nearest edge of the 
entrance is not less than the minimum clear distance speci- 
fied in Table 110.34(A) for equipment operating at that 
voltage and in that condition. 

(2) Guarding. Where bare energized parts at any voltage 
or insulated energized parts above 600 volts, nominal, to 
ground are located adjacent to such entrance, they shall be 
suitably guarded. 

(B) Access. Permanent ladders or stairways shall be pro- 
vided to give safe access to the working space around elec- 
tric equipment installed on platforms, balconies, or mezza- 
nine floors or in attic or roof rooms or spaces. 

110.34 Work Space and Guarding. 

(A) Working Space. Except as elsewhere required or per- 
mitted in this Code, the minimum clear working space in 
the direction of access to live parts of electrical equipment 
shall not be less than specified in Table 110.34(A). Dis- 
tances shall be measured from the live parts, if such are 
exposed, or from the enclosure front or opening if such are 
enclosed. 

Exception: Working space shall not be required in back of 
equipment such as dead-front switchboards or control as- 
semblies where there are no renewable or adjustable parts 
(such as fuses or switches) on the back and where all con- 
nections are accessible from locations other than the back. 
Where rear access is required to work on de-energized 
parts on the back of enclosed equipment, a minimum work- 
ing space of 750 mm (30 in.) horizontally shall be provided. 

(B) Separation from Low- Voltage Equipment. Where 
switches, cutouts, or other equipment operating at 600 
volts, nominal, or less are installed in a room or enclosure 
where there are exposed live parts or exposed wiring oper- 
ating at over 600 volts, nominal, the high-voltage equip- 
ment shall be effectively separated from the space occupied 
by the low-voltage equipment by a suitable partition, fence, 
or screen. 

Exception: Switches or other equipment operating at 600 
volts, nominal, or less and serving only equipment within 
the high-voltage vault, room, or enclosure shall be permit- 
ted to be installed in the high-voltage enclosure, room, or 
vault if accessible to qualified persons only. 

(C) Locked Rooms or Enclosures. The entrances to all 
buildings, rooms, or enclosures containing exposed live 
parts or exposed conductors operating at over 600 volts, 
nominal, shall be kept locked unless such entrances are 
under the observation of a qualified person at all times. 



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ARTICLE 110 — REQUIREMENTS FOR ELECTRICAL INSTALLATIONS 



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Table 110.34(A) Minimum Depth of Clear Working Space at 
Electrical Equipment 

Minimum Clear Distance 

Nominal Voltage 

to Ground Condition 1 Condition 2 Condition 3 



601-2500 V 
2501-9000 V 
9001-25,000 V 
25,001V-75 kV 
Above 75 kV 



900 mm (3 ft) 
1.2 m (4 ft) 
1.5 m (5 ft) 
1.8 m (6 ft) 
2.5 m (8 ft) 



1.2 m (4 ft) 
1.5 m (5 ft) 
1.8 m (6 ft) 
2.5 m (8 ft) 
3.0 m (10 ft) 



1.5 m (5 ft) 
1.8 m (6 ft) 
2.8 m (9 ft) 
3.0 m (10 ft) 
3.7 m (12 ft) 



Note: Where the conditions are as follows: 

Condition 1 — Exposed live parts on one side and no live or 

grounded parts on the other side of the working space, or exposed live 

parts on both sides effectively guarded by suitable wood or other 

insulating materials. Insulated wire or insulated busbars operating at 

not over 300 volts shall not be considered live parts. 

Condition 2 — Exposed live parts on one side and grounded parts on 

the other side. Concrete, brick, or tile walls shall be considered as 

grounded surfaces. 

Condition 3 — Exposed live parts on both sides of the work space 

(not guarded as provided in Condition 1) with the operator between. 



Where the voltage exceeds 600 volts, nominal, perma- 
nent and conspicuous warning signs shall be provided, 
reading as follows: 

DANGER — HIGH VOLTAGE — KEEP OUT 

(D) Illumination. Illumination shall be provided for all 
working spaces about electrical equipment. The lighting 
outlets shall be arranged so that persons changing lamps or 
making repairs on the lighting system are not endangered 
by live parts or other equipment. 

The points of control shall be located so that persons 
are not likely to come in contact with any live part or 
moving part of the equipment while turning on the lights. 

(E) Elevation of Unguarded Live Parts. Unguarded live 
parts above working space shall be maintained at elevations 
not less than required by Table 110.34(E). 



Table 110.34(E) Elevation of Unguarded Live Parts Above 
Working Space 



Elevation 



Nominal Voltage 
Between Phases 



ft 



601-7500 V 
7501-35,000 V 
Over 35 kV 



2.8 9 

2.9 9Vi 
2.9 m + 9 L / 2 ft + 
9.5 mm/kV 0.37 in./kV 
above 35 above 35 



(F) Protection of Service Equipment, Metal-Enclosed 
Power Switchgear, and Industrial Control Assemblies. 

Pipes or ducts foreign to the electrical installation and re- 
quiring periodic maintenance or whose malfunction would 
endanger the operation of the electrical system shall not be 
located in the vicinity of the service equipment, metal- 
enclosed power switchgear, or industrial control assemblies. 
Protection shall be provided where necessary to avoid damage 
from condensation leaks and breaks in such foreign systems. 
Piping and other facilities shall not be considered foreign if 
provided for fire protection of the electrical installation. 

110.36 Circuit Conductors. Circuit conductors shall be 
permitted to be installed in raceways; in cable trays; as 
metal-clad cable, as bare wire, cable, and busbars; or as 
Type MV cables or conductors as provided in 300.37, 
300.39, 300.40, and 300.50. Bare live conductors shall con- 
form with 490.24. 

Insulators, together with their mounting and conductor 
attachments, where used as supports for wires, single- 
conductor cables, or busbars, shall be capable of safely 
withstanding the maximum magnetic forces that would pre- 
vail when two or more conductors of a circuit were sub- 
jected to short-circuit current. 

Open runs of insulated wires and cables that have a bare 
lead sheath or a braided outer covering shall be supported 
in a manner designed to prevent physical damage to the 
braid or sheath. Supports for lead-covered cables shall be 
designed to prevent electrolysis of the sheath. 

110.40 Temperature Limitations at Terminations. Con- 
ductors shall be permitted to be terminated based on the 
90°C (194°F) temperature rating and ampacity as given in 
Tables 310.67 through 310.86, unless otherwise identified. 

IV. Tunnel Installations Over 600 Volts, Nominal 
110.51 General. 

(A) Covered. The provisions of this part shall apply to the 
installation and use of high-voltage power distribution and 
utilization equipment that is portable, mobile, or both, such 
as substations, trailers, cars, mobile shovels, draglines, 
hoists, drills, dredges, compressors, pumps, conveyors, and 
underground excavators, and the like. 

(B) Other Articles. The requirements of this part shall be 
additional to, or amendatory of, those prescribed in Articles 
100 through 490 of this Code. Special attention shall be 
paid to Article 250. 

(C) Protection Against Physical Damage. Conductors 
and cables in tunnels shall be located above the tunnel floor 
and so placed or guarded to protect them from physical 
damage. 



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ARTICLE 110 — REQUIREMENTS FOR ELECTRICAL INSTALLATIONS 



110.52 Overcurrent Protection. Motor-operated equip- 
ment shall be protected from overcurrent in accordance 
with Article 430. Transformers shall be protected from 
overcurrent in accordance with Article 450. 

110.53 Conductors. High-voltage conductors in tunnels 
shall be installed in metal conduit or other metal raceway, 
Type MC cable, or other approved multiconductor cable. 
Multiconductor portable cable shall be permitted to supply 
mobile equipment. 

110.54 Bonding and Equipment Grounding Conduc- 
tors. 

(A) Grounded and Bonded. All non-current-carrying 
metal parts of electric equipment and all metal raceways 
and cable sheaths shall be effectively grounded and bonded 
to all metal pipes and rails at the portal and at intervals not 
exceeding 300 m (1000 ft) throughout the tunnel. 

(B) Equipment Grounding Conductors. An equipment 
grounding conductor shall be run with circuit conductors 
inside the metal raceway or inside the multiconductor cable 
jacket. The equipment grounding conductor shall be per- 
mitted to be insulated or bare. 

110.55 Transformers, Switches, and Electrical Equipment 

All transformers, switches, motor controllers, motors, rec- 



tifiers, and other equipment installed below ground shall be 
protected from physical damage by location or guarding. 

110.56 Energized Parts. Bare terminals of transformers, 
switches, motor controllers, and other equipment shall be 
enclosed to prevent accidental contact with energized parts. 

110.57 Ventilation System Controls. Electrical controls 
for the ventilation system shall be arranged so that the 
airflow can be reversed. 

110.58 Disconnecting Means. A switch or circuit breaker 
that simultaneously opens all ungrounded conductors of the 
circuit shall be installed within sight of each transformer or 
motor location for disconnecting the transformer or motor. 
The switch or circuit breaker for a transformer shall have 
an ampere rating not less than the ampacity of the trans- 
former supply conductors. The switch or circuit breaker for 
a motor shall comply with the applicable requirements of 
Article 430. 

110.59 Enclosures. Enclosures for use in tunnels shall be 
dripproof, weatherproof, or submersible as required by the 
environmental conditions. Switch or contactor enclosures 
shall not be used as junction boxes or as raceways for 
conductors feeding through or tapping off to other switches, 
unless special designs are used to provide adequate space 
for this purpose. 



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ARTICLE 200 — USE AND IDENTIFICATION OF GROUNDED CONDUCTORS 



70-49 



Chapter 2 Wiring and Protection 



ARTICLE 200 

Use and Identification of Grounded 

Conductors 

200.1 Scope. This article provides requirements for the 
following: 

(1) Identification of terminals 

(2) Grounded conductors in premises wiring systems 

(3) Identification of grounded conductors 

FPN: See Article 100 for definitions of Grounded Conduc- 
tor and Grounding Conductor. 

200.2 General. All premises wiring systems, other than 
circuits and systems exempted or prohibited by 210.10, 
215.7, 250.21, 250.22, 250.162, 503.13, 517.63, 668.11, 
668.21, and 690.41, Exception, shall have a grounded con- 
ductor that is identified in accordance with 200.6. 

The grounded conductor, where insulated, shall have 
insulation that is (1) suitable, other than color, for any un- 
grounded conductor of the same circuit on circuits of less 
than 1000 volts or impedance grounded neutral systems of 
1 kV and over, or (2) rated not less than 600 volts for 
solidly grounded neutral systems of 1 kV and over as de- 
scribed in 250.184(A). 

200.3 Connection to Grounded System. Premises wiring 
shall not be electrically connected to a supply system un- 
less the latter contains, for any grounded conductor of the 
interior system, a corresponding conductor that is 
grounded. For the purpose of this section, electrically con- 
nected shall mean connected so as to be capable of carrying 
current, as distinguished from connection through electro- 
magnetic induction. 

200.6 Means of Identifying Grounded Conductors. 

(A) Sizes 6 AWG or Smaller. An insulated grounded con- 
ductor of 6 AWG or smaller shall be identified by a con- 
tinuous white or gray outer finish or by three continuous 
white stripes on other than green insulation along its entire 
length. Wires that have their outer covering finished to 
show a white or gray color but have colored tracer threads 
in the braid identifying the source of manufacture shall be 
considered as meeting the provisions of this section. Insu- 
lated grounded conductors shall also be permitted to be 
identified as follows: 

(1) The grounded conductor of a mineral-insulated, metal- 
sheathed cable shall be identified at the time of instal- 
lation by distinctive marking at its terminations. 



(2) A single-conductor, sunlight-resistant, outdoor-rated 
cable used as a grounded conductor in photovoltaic 
power systems as permitted by 690.31 shall be identi- 
fied at the time of installation by distinctive white 
marking at all terminations. 

(3) Fixture wire shall comply with the requirements for 
grounded conductor identification as specified in 402.8 

(4) For aerial cable, the identification shall be as above, or 
by means of a ridge located on the exterior of the cable 
so as to identify it. 

(B) Sizes Larger Than 6 AWG. An insulated grounded 
conductor larger than 6 AWG shall be identified either by a 
continuous white or gray outer finish or by three continuous 
white stripes on other than green insulation along its entire 
length or at the time of installation by a distinctive white 
marking at its terminations. This marking shall encircle the 
conductor or insulation. 

(C) Flexible Cords. An insulated conductor that is in- 
tended for use as a grounded conductor, where contained 
within a flexible cord, shall be identified by a white or gray 
outer finish or by three continuous white stripes on other 
than green insulation or by methods permitted by 400.22. 

(D) Grounded Conductors of Different Systems. Where 
conductors of different systems are installed in the same 
raceway, cable, box, auxiliary gutter, or other type of en- 
closure, one system grounded conductor, if required, shall 
have an outer covering conforming to 200.6(A) or 
200.6(B). Each other system grounded conductor shall have 
an outer covering of white with a readily distinguishable, 
different colored stripe other than green running along the 
insulation, or shall have other and different means of iden- 
tification as allowed by 200.6(A) or (B) that will distin- 
guish each system grounded conductor. 

(E) Grounded Conductors of Multiconductor Cables. 

The insulated grounded conductors in a multiconductor 
cable shall be identified by a continuous white or gray outer 
finish or by three continuous white stripes on other than 
green insulation along its entire length. Multiconductor flat 
4 AWG or larger shall be permitted to employ an external 
ridge on the grounded conductor. 

Exception No. 1: Where the conditions of maintenance and 
supervision ensure that only qualified persons service the 
installation, grounded conductors in multiconductor cables 
shall be permitted to be permanently identified at their ter- 
minations at the time of installation by a distinctive white 
marking or other equally effective means. 

Exception No. 2: The grounded conductor of a multicon- 
ductor varnished-cloth-insulated cable shall be permitted 



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ARTICLE 200 — USE AND IDENTIFICATION OF GROUNDED CONDUCTORS 



to be identified at its terminations at the time of installation 
by a distinctive white marking or other equally effective 
means. 

FPN: The color gray may have been used in the past as an 
ungrounded conductor. Care should be taken when working 
on existing systems. 

200.7 Use of Insulation of a White or Gray Color or 
with Three Continuous White Stripes. 

(A) General. The following shall be used only for the 
grounded circuit conductor, unless otherwise permitted in 
200.7(B) and (C): 

(1) A conductor with continuous white or gray covering 

(2) A conductor with three continuous white stripes on 
other than green insulation 

(3) A marking of white or gray color at the termination 

(B) Circuits of Less Than 50 Volts. A conductor with 
white or gray color insulation or three continuous white 
stripes or having a marking of white or gray at the termi- 
nation for circuits of less than 50 volts shall be required to 
be grounded only as required by 250.20(A). 

(C) Circuits of 50 Volts or More. The use of insulation 
that is white or gray or that has three continuous white 
stripes for other than a grounded conductor for circuits 
of 50 volts or more shall be permitted only as in (1) 
through (3). 

(1) If part of a cable assembly and where the insulation is 
permanently reidentified to indicate its use as an un- 
grounded conductor, by painting or other effective 
means at its termination, and at each location where the 
conductor is visible and accessible. 

(2) Where a cable assembly contains an insulated conduc- 
tor for single-pole, 3-way or 4-way switch loops and 
the conductor with white or gray insulation or a mark- 
ing of three continuous white stripes is used for the 
supply to the switch but not as a return conductor from 
the switch to the switched outlet. In these applications, 
the conductor with white or gray insulation or with 
three continuous white stripes shall be permanently re- 
identified to indicate its use by painting or other effec- 
tive means at its terminations and at each location 
where the conductor is visible and accessible. 

(3) Where a flexible cord, having one conductor identified 
by a white or gray outer finish or three continuous 
white stripes or by any other means permitted by 
400.22, is used for connecting an appliance or equip- 
ment permitted by 400.7. This shall apply to flexible 
cords connected to outlets whether or not the outlet is 
supplied by a circuit that has a grounded conductor. 

FPN: The color gray may have been used in the past as an 
ungrounded conductor. Care should be taken when working 
on existing systems. 



200.9 Means of Identification of Terminals. The identifi- 
cation of terminals to which a grounded conductor is to be 
connected shall be substantially white in color. The identi- 
fication of other terminals shall be of a readily distinguish- 
able different color. 

Exception: Where the conditions of maintenance and su- 
pervision ensure that only qualified persons service the 
installations, terminals for grounded conductors shall be 
permitted to be permanently identified at the time of instal- 
lation by a distinctive white marking or other equally effec- 
tive means. 

200.10 Identification of Terminals. 

(A) Device Terminals. All devices, excluding panel- 
boards, provided with terminals for the attachment of con- 
ductors and intended for connection to more than one side 
of the circuit shall have terminals properly marked for iden- 
tification, unless the electrical connection of the terminal 
intended to be connected to the grounded conductor is 
clearly evident. 

Exception: Terminal identification shall not be required for 
devices that have a normal current rating of over 30 am- 
peres, other than polarized attachment plugs and polarized 
receptacles for attachment plugs as required in 200.10(B). 

(B) Receptacles, Plugs, and Connectors. Receptacles, 
polarized attachment plugs, and cord connectors for plugs 
and polarized plugs shall have the terminal intended for 
connection to the grounded conductor identified as follows: 

(1) Identification shall be by a metal or metal coating that 
is substantially white in color or by the word white or 
the letter W located adjacent to the identified terminal. 

(2) If the terminal is not visible, the conductor entrance 
hole for the connection shall be colored white or 
marked with the word white or the letter W. 

FPN: See 250.126 for identification of wiring device 
equipment grounding conductor terminals. 

(C) Screw Shells. For devices with screw shells, the ter- 
minal for the grounded conductor shall be the one con- 
nected to the screw shell. 

(D) Screw Shell Devices with Leads. For screw shell de- 
vices with attached leads, the conductor attached to the 
screw shell shall have a white or gray finish. The outer 
finish of the other conductor shall be of a solid color that 
will not be confused with the white or gray finish used to 
identify the grounded conductor. 

FPN: The color gray may have been used in the past as an 
ungrounded conductor. Care should be taken when working 
on existing systems. 

(E) Appliances. Appliances that have a single-pole switch 
or a single-pole overcurrent device in the line or any line- 



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ARTICLE 210 — BRANCH CIRCUITS 



70-51 



connected screw shell landholders, and that are to be con- 
nected by (1) a permanent wiring method or (2) field- 
installed attachment plugs and cords with three or more 
wires (including the equipment grounding conductor), shall 
have means to identify the terminal for the grounded circuit 
conductor (if any). 

200.11 Polarity of Connections. No grounded conductor 
shall be attached to any terminal or lead so as to reverse the 
designated polarity. 



ARTICLE 210 
Branch Circuits 



Table 210.2 Specific-Purpose Branch Circuits 



I. General Provisions 

210.1 Scope. This article covers branch circuits except for 
branch circuits that supply only motor loads, which are 
covered in Article 430. Provisions of this article and Article 
430 apply to branch circuits with combination loads. 

210.2 Other Articles for Specific-Purpose Branch 
Circuits. Branch circuits shall comply with this article and 
also with the applicable provisions of other articles of this 
Code. The provisions for branch circuits supplying equip- 
ment in Table 210.2 amend or supplement the provisions in 
this article and shall apply to branch circuits referred to 
therein. 

210.3 Rating. Branch circuits recognized by this article 
shall be rated in accordance with the maximum permitted 
ampere rating or setting of the overcurrent device. The rat- 
ing for other than individual branch circuits shall be 15, 20, 
30, 40, and 50 amperes. Where conductors of higher am- 
pacity are used for any reason, the ampere rating or setting 
of the specified overcurrent device shall determine the cir- 
cuit rating. 

Exception: Multioutlet branch circuits greater than 50 am- 
peres shall be permitted to supply nonlighting outlet loads 
on industrial premises where conditions of maintenance 
and supervision ensure that only qualified persons service 
the equipment. 

210.4 Multiwire Branch Circuits. 

(A) General. Branch circuits recognized by this article 
shall be permitted as multiwire circuits. A multiwire branch 
circuit shall be permitted to be considered as multiple cir- 
cuits. All conductors shall originate from the same panel- 
board. 



Equipment 


Article 


Section 


Air-conditioning and 




440.6, 440.31, 


refrigerating equipment 




440.32 


Audio signal processing, 




640.8 


amplification, and 






reproduction equipment 






Busways 




368 


Circuits and equipment 


720 




operating at less than 50 






volts 






Central heating equipment 




422.12 


other than fixed electric 






space-heating equipment 






Class 1, Class 2, and Class 3 


725 




remote-control, signaling, 






and power-limited circuits 






Closed-loop and programmed 


780 




power distribution 






Cranes and hoists 




610.42 


Electric signs and outline 




600.6 


lighting 






Electric welders 


630 




Elevators, dumbwaiters, 




620.61 


escalators, moving walks, 






wheelchair lifts, and 






stairway chair lifts 






Fire alarm systems 


760 




Fixed electric heating 




427.4 


equipment for pipelines and 






vessels 






Fixed electric space-heating 




424.3 


equipment 






Fixed outdoor electric deicing 




426.4 


and snow-melting 






equipment 






Information technology 




645.5 


equipment 






Infrared lamp industrial 




422.48, 424.3 


heating equipment 






Induction and dielectric 


665 




heating equipment 






Marinas and boatyards 




555.19 


Mobile homes, manufactured 


550 




homes, and mobile home 






parks 






Motion picture and television 


530 




studios and similar 






locations 






Motors, motor circuits, and 


430 




controllers 






Pipe organs 




650.7 


Recreational vehicles and 


551 




recreational vehicle parks 






Switchboards and panelboards 




408.32 


Theaters, audience areas of 




520.41, 520.52, 


motion picture and 




520.62 


television studios, and 






similar locations 






X-ray equipment 




660.2, 517.73 



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ARTICLE 210 — BRANCH CIRCUITS 



FPN: A 3-phase, 4-wire, wye-connected power system 
used to supply power to nonlinear loads may necessitate 
that the power system design allow for the possibility of 
high harmonic neutral currents. 

(B) Dwelling Units. In dwelling units, a multiwire branch 
circuit supplying more than one device or equipment on the 
same yoke shall be provided with a means to disconnect 
simultaneously all ungrounded conductors at the panel- 
board where the branch circuit originated. 

(C) Line-to-Neutral Loads. Multiwire branch circuits 
shall supply only line-to-neutral loads. 

Exception No. 1: A multiwire branch circuit that supplies 
only one utilization equipment. 

Exception No. 2: Where all ungrounded conductors of the 
multiwire branch circuit are opened simultaneously by the 
branch-circuit overcurrent device. 

FPN: See 300.13(B) for continuity of grounded conductor 
on multiwire circuits. 

(D) Identification of Ungrounded Conductors. Where 
more than one nominal voltage system exists in a building, 
each ungrounded conductor of a multiwire branch circuit, 
where accessible, shall be identified by phase and system. 
This means of identification shall be permitted to be by 
separate color coding, marking tape, tagging, or other ap- 
proved means and shall be permanently posted at each 
branch-circuit panelboard. 

210.5 Identification for Branch Circuits. 

(A) Grounded Conductor. The grounded conductor of a 
branch circuit shall be identified in accordance with 200.6. 

(B) Equipment Grounding Conductor. The equipment 
grounding conductor shall be identified in accordance with 
250.119. 

210.6 Branch-Circuit Voltage Limitations. The nominal 
voltage of branch circuits shall not exceed the values per- 
mitted by 210.6(A) through (E). 

(A) Occupancy Limitation. In dwelling units and guest 
rooms of hotels, motels, and similar occupancies, the volt- 
age shall not exceed 120 volts, nominal, between conduc- 
tors that supply the terminals of the following: 

(1) Luminaires (lighting fixtures) 

(2) Cord-and-plug-connected loads 1440 volt-amperes, 
nominal, or less or less than l A hp 

(B) 120 Volts Between Conductors. Circuits not exceed- 
ing 120 volts, nominal, between conductors shall be permit- 
ted to supply the following: 



(1) The terminals of landholders applied within their volt- 
age ratings 

(2) Auxiliary equipment of electric-discharge lamps 

(3) Cord-and-plug-connected or permanently connected 
utilization equipment 

(C) 277 Volts to Ground. Circuits exceeding 120 volts, 
nominal, between conductors and not exceeding 277 volts, 
nominal, to ground shall be permitted to supply the follow- 
ing: 

(1) Listed electric-discharge luminaires (lighting fixtures) 

(2) Listed incandescent luminaires (lighting fixtures), 
where supplied at 120 volts or less from the output of a 
stepdown autotransformer that is an integral component 
of the luminaire (fixture) and the outer shell terminal is 
electrically connected to a grounded conductor of the 
branch circuit 

(3) Luminaires (lighting fixtures) equipped with mogul- 
base screw shell lampholders 

(4) Lampholders, other than the screw shell type, applied 
within their voltage ratings 

(5) Auxiliary equipment of electric-discharge lamps 

(6) Cord-and-plug-connected or permanently connected 
utilization equipment 

(D) 600 Volts Between Conductors. Circuits exceeding 
277 volts, nominal, to ground and not exceeding 600 volts, 
nominal, between conductors shall be permitted to supply 
the following: 

(1) The auxiliary equipment of electric-discharge lamps 
mounted in permanently installed luminaires (fixtures) 
where the luminaires (fixtures) are mounted in accor- 
dance with one of the following: 

a. Not less than a height of 6.7 m (22 ft) on poles or 
similar structures for the illumination of outdoor ar- 
eas such as highways, roads, bridges, athletic fields, 
or parking lots 

b. Not less than a height of 5.5 m (18 ft) on other 
structures such as tunnels 

(2) Cord-and-plug-connected or permanently connected 
utilization equipment 

FPN: See 410.78 for auxiliary equipment limitations. 

Exception No. 1 to (B), (C), and (D): For lampholders of 
infrared industrial heating appliances as provided in 
422.14. 

Exception No. 2 to (B), (C), and (D): For railway proper- 
ties as described in 110.19. 

(E) Over 600 Volts Between Conductors. Circuits ex- 
ceeding 600 volts, nominal, between conductors shall be 
permitted to supply utilization equipment in installations 
where conditions of maintenance and supervision ensure 
that only qualified persons service the installation. 



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ARTICLE 210 — BRANCH CIRCUITS 



70-53 



210.7 Branch Circuit Receptacle Requirements. 

(A) Receptacle Outlet Location. Receptacle outlets shall 
be located in branch circuits in accordance with Part III of 
Article 210. 

(B) Receptacle Requirements. Specific requirements for 
receptacles are covered in Article 406. 

(C) Multiple Branch Circuits. Where more than one 
branch circuit supplies more than one receptacle on the 
same yoke, a means to simultaneously disconnect the un- 
grounded conductors supplying those receptacles shall be 
provided at the panelboard where the branch circuits origi- 
nated. 

210.8 Ground-Fault Circuit-Interrupter Protection for 
Personnel. 

FPN: See 215.9 for ground-fault circuit-interrupter protec- 
tion for personnel on feeders. 

(A) Dwelling Units. All 125-volt, single-phase, 15- and 
20-ampere receptacles installed in the locations specified in 
(1) through (8) shall have ground-fault circuit-interrupter 
protection for personnel. 

(1) Bathrooms 

(2) Garages, and also accessory buildings that have a floor 
located at or below grade level not intended as habit- 
able rooms and limited to storage areas, work areas, 
and areas of similar use 

Exception No. 1: Receptacles that are not readily accessible. 

Exception No. 2: A single receptacle or a duplex recep- 
tacle for two appliances located within dedicated space for 
each appliance that, in normal use, is not easily moved 
from one place to another and that is cord-and-plug con- 
nected in accordance with 400. 7(A)(6), (A)(7), or (A)(8). 

Receptacles installed under the exceptions to 
210.8(A)(2) shall not be considered as meeting the require- 
ments of 210.52(G). 

(3) Outdoors 

Exception: Receptacles that are not readily accessible and 
are supplied by a dedicated branch circuit for electric 
snow-melting or deicing equipment shall be permitted to be 
installed in accordance with the applicable provisions of 
Article 426. 

(4) Crawl spaces — at or below grade level 

(5) Unfinished basements — for purposes of this section, 
unfinished basements are defined as portions or areas of 
the basement not intended as habitable rooms and lim- 
ited to storage areas, work areas, and the like 

Exception No. 1: Receptacles that are not readily accessible. 



Exception No. 2: A single receptacle or a duplex recep- 
tacle for two appliances located within dedicated space for 
each appliance that, in normal use, is not easily moved 
from one place to another and that is cord-and-plug con- 
nected in accordance with 400.7(A)(6), (A)(7), or (A)(8). 

Exception No. 3: A receptacle supplying only a perma- 
nently installed fire alarm or burglar alarm system shall 
not be required to have ground-fault circuit-interrupter 
protection. 

Receptacles installed under the exceptions to 
210.8(A)(5) shall not be considered as meeting the require- 
ments of 210.52(G). 

(6) Kitchens — where the receptacles are installed to serve 
the countertop surfaces 

(7) Wet bar sinks — where the receptacles are installed to 
serve the countertop surfaces and are located within 1.8 
m (6 ft) of the outside edge of the wet bar sink. 

(8) Boathouses 

(B) Other Than Dwelling Units. All 125-volt, single- 
phase, 15- and 20-ampere receptacles installed in the loca- 
tions specified in (1), (2), and (3) shall have ground-fault 
circuit-interrupter protection for personnel: 

(1) Bathrooms 

(2) Rooftops 

Exception to 2: Receptacles that are not readily accessible 
and are supplied from a dedicated branch circuit for elec- 
tric snow-melting or deicing equipment shall be permitted 
to be installed in accordance with the applicable provisions 
of Article 426. 

(3) Kitchens 

210.9 Circuits Derived from Autotransformers. Branch 
circuits shall not be derived from autotransformers unless 
the circuit supplied has a grounded conductor that is elec- 
trically connected to a grounded conductor of the system 
supplying the autotransformer. 

Exception No. 1: An autotransformer shall be permitted 
without the connection to a grounded conductor where 
transforming from a nominal 208 volts to a nominal 240- 
volt supply or similarly from 240 volts to 208 volts. 

Exception No. 2: In industrial occupancies, where condi- 
tions of maintenance and supervision ensure that only 
qualified persons service the installation, autotransformers 
shall be permitted to supply nominal 600-volt loads from 
nominal 480-volt systems, and 480-volt loads from nominal 
600-volt systems, without the connection to a similar 
grounded conductor. 

210.10 Ungrounded Conductors Tapped from Grounded 
Systems. Two-wire dc circuits and ac circuits of two or more 
ungrounded conductors shall be permitted to be tapped from 



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70-54 



ARTICLE 210 — BRANCH CIRCUITS 



the ungrounded conductors of circuits that have a grounded 
neutral conductor. Switching devices in each tapped circuit 
shall have a pole in each ungrounded conductor. All poles of 
multipole switching devices shall manually switch together 
where such switching devices also serve as a disconnecting 
means as required by the following: 

(1) 410.48 for double-pole switched lampholders 

(2) 410.54(B) for electric-discharge lamp auxiliary equip- 
ment switching devices 

(3) 422.31(B) for an appliance 

(4) 424.20 for a fixed electric space-heating unit 

(5) 426.51 for electric deicing and snow-melting equip- 
ment 

(6) 430.85 for a motor controller 

(7) 430.103 for a motor 

210.11 Branch Circuits Required. Branch circuits for 
lighting and for appliances, including motor-operated appli- 
ances, shall be provided to supply the loads computed in 
accordance with 220.3. In addition, branch circuits shall be 
provided for specific loads not covered by 220.3 where 
required elsewhere in this Code and for dwelling unit loads 
as specified in 210.11(C). 

(A) Number of Branch Circuits. The minimum number 
of branch circuits shall be determined from the total com- 
puted load and the size or rating of the circuits used. In all 
installations, the number of circuits shall be sufficient to 
supply the load served. In no case shall the load on any 
circuit exceed the maximum specified by 220.4. 

(B) Load Evenly Proportioned Among Branch Circuits. 

Where the load is computed on a volt- amperes/square 
meter or square foot basis, the wiring system up to and 
including the branch-circuit panelboard(s) shall be provided 
to serve not less than the calculated load. This load shall be 
evenly proportioned among multioutlet branch circuits 
within the panelboard(s). Branch-circuit overcurrent de- 
vices and circuits shall only be required to be installed to 
serve the connected load. 

(C) Dwelling Units. 

(1) Small-Appliance Branch Circuits. In addition to the 
number of branch circuits required by other parts of this 
section, two or more 20-ampere small-appliance branch cir- 
cuits shall be provided for all receptacle outlets specified by 
210.52(B). 

(2) Laundry Branch Circuits. In addition to the number 
of branch circuits required by other parts of this section, at 
least one additional 20-ampere branch circuit shall be pro- 
vided to supply the laundry receptacle outlet(s) required by 
210.52(F). This circuit shall have no other outlets. 



(3) Bathroom Branch Circuits. In addition to the number 
of branch circuits required by other parts of this section, at 
least one 20-ampere branch circuit shall be provided to 
supply the bathroom receptacle outlet(s). Such circuits shall 
have no other outlets. 

Exception: Where the 20-ampere circuit supplies a single 
bathroom, outlets for other equipment within the same 
bathroom shall be permitted to be supplied in accordance 
with 210.23(A). 

FPN: See Examples D1(A), D1(B), D2(B), and D4(A) in 
Annex D. 

210.12 Arc-Fault Circuit-Interrupter Protection. 

(A) Definition. An arc-fault circuit interrupter is a device 
intended to provide protection from the effects of arc faults 
by recognizing characteristics unique to arcing and by func- 
tioning to de-energize the circuit when an arc fault is de- 
tected. 

(B) Dwelling Unit Bedrooms. All branch circuits that sup- 
ply 125- volt, single-phase, 15- and 20-ampere outlets in- 
stalled in dwelling unit bedrooms shall be protected by an 
arc-fault circuit interrupter listed to provide protection of 
the entire branch circuit. 

II. Branch-Circuit Ratings 

210.19 Conductors — Minimum Ampacity and Size. 

(A) Branch Circuits Not More Than 600 Volts. 

(1) General. Branch-circuit conductors shall have an am- 
pacity not less than the maximum load to be served. Where 
a branch circuit supplies continuous loads or any combina- 
tion of continuous and noncontinuous loads, the minimum 
branch-circuit conductor size, before the application of any 
adjustment or correction factors, shall have an allowable 
ampacity not less than the noncontinuous load plus 
125 percent of the continuous load. 

Exception: Where the assembly, including the overcurrent 
devices protecting the branch circuit(s), is listed for opera- 
tion at 100 percent of its rating, the allowable ampacity of 
the branch circuit conductors shall be permitted to be not 
less than the sum of the continuous load plus the noncon- 
tinuous load. 

FPN No. 1: See 310.15 for ampacity ratings of conductors. 

FPN No. 2: See Part II of Article 430 for minimum rating 
of motor branch-circuit conductors. 

FPN No. 3: See 310.10 for temperature limitation of con- 
ductors. 

FPN No. 4: Conductors for branch circuits as defined in 
Article 100, sized to prevent a voltage drop exceeding 
3 percent at the farthest outlet of power, heating, and light- 



2002 Edition 



NATIONAL ELECTRICAL CODE 



ARTICLE 210 — BRANCH CIRCUITS 



70-55 



ing loads, or combinations of such loads, and where the 
maximum total voltage drop on both feeders and branch 
circuits to the farthest outlet does not exceed 5 percent, 
provide reasonable efficiency of operation. See 215.2 for 
voltage drop on feeder conductors. 

(2) Multioutlet Branch Circuits. Conductors of branch 
circuits supplying more than one receptacle for cord-and- 
plug-connected portable loads shall have an ampacity of 
not less than the rating of the branch circuit. 

(3) Household Ranges and Cooking Appliances. Branch- 
circuit conductors supplying household ranges, wall-mounted 
ovens, counter-mounted cooking units, and other household 
cooking appliances shall have an ampacity not less than the 
rating of the branch circuit and not less than the maximum 
load to be served. For ranges of 8% kW or more rating, the 
minimum branch-circuit rating shall be 40 amperes. 

Exception No. 1: Tap conductors supplying electric ranges, 
wall-mounted electric ovens, and counter-mounted electric 
cooking units from a 50-ampere branch circuit shall have 
an ampacity of not less than 20 and shall be sufficient for 
the load to be served. The taps shall not be longer than 
necessary for servicing the appliance. 

Exception No. 2: The neutral conductor of a 3 -wire branch 
circuit supplying a household electric range, a wall- 
mounted oven, or a counter-mounted cooking unit shall be 
permitted to be smaller than the ungrounded conductors 
where the maximum demand of a range of 8 3 /t kW or more 
rating has been computed according to Column C of Table 
220.19, but shall have an ampacity of not less than 70 per- 
cent of the branch-circuit rating and shall not be smaller 
than 10 AWG. 

(4) Other Loads. Branch-circuit conductors that supply 
loads other than those specified in 210.2 and other than 
cooking appliances as covered in 210.19(A)(3) shall have 
an ampacity sufficient for the loads served and shall not be 
smaller than 14 AWG. 

Exception No. 1: Tap conductors shall have an ampacity 
sufficient for the load served. In addition, they shall have an 
ampacity of not less than 15 for circuits rated less than 40 
amperes and not less than 20 for circuits rated at 40 or 50 
amperes and only where these tap conductors supply any of 
the following loads: 

(a) Individual lampholders or luminaires (fixtures) with 
taps extending not longer than 450 mm (18 in.) beyond 
any portion of the lampholder or luminaire (fixture). 

(b) A fixture having tap conductors as provided in 410.67. 

(c) Individual outlets, other than receptacle outlets, with 
taps not over 450 mm (18 in.) long. 

(d) Infrared lamp industrial heating appliances. 

(e) Nonheating leads of deicing and snow-melting cables 
and mats. 



Exception No. 2: Fixture wires and flexible cords shall be 
permitted to be smaller than 14 AWG as permitted by 
240.5. 

(B) Branch Circuits Over 600 Volts. The ampacity of 
conductors shall be in accordance with 310.15 and 310.60 
as applicable. Branch-circuit conductors over 600 volts 
shall be sized in accordance with 210.19(B)(1) or (B)(2). 

(1) General. The ampacity of branch-circuit conductors 
shall not be less than 125 percent of the designed potential 
load of utilization equipment that will be operated simulta- 
neously. 

(2) Supervised Installations. For supervised installations, 
branch-circuit conductor sizing shall be permitted to be de- 
termined by qualified persons under engineering supervi- 
sion. Supervised installations are defined as those portions 
of a facility where all of the following conditions are met: 

(1) Conditions of design and installation are provided un- 
der engineering supervision. 

(2) Qualified persons with documented training and expe- 
rience in over 600-volt systems provide maintenance, 
monitoring, and servicing of the system. 

210.20 Overcurrent Protection. Branch-circuit conduc- 
tors and equipment shall be protected by overcurrent pro- 
tective devices that have a rating or setting that complies 
with 210.20(A) through (D). 

(A) Continuous and Noncontinuous Loads. Where a 
branch circuit supplies continuous loads or any combina- 
tion of continuous and noncontinuous loads, the rating of 
the overcurrent device shall not be less than the noncon- 
tinuous load plus 125 percent of the continuous load. 

Exception: Where the assembly, including the overcurrent 
devices protecting the branch circuit(s), is listed for opera- 
tion at 100 percent of its rating, the ampere rating of the 
overcurrent device shall be permitted to be not less than the 
sum of the continuous load plus the noncontinuous load. 

(B) Conductor Protection. Conductors shall be protected 
in accordance with 240.4. Flexible cords and fixture wires 
shall be protected in accordance with 240.5. 

(C) Equipment. The rating or setting of the overcurrent 
protective device shall not exceed that specified in the ap- 
plicable articles referenced in 240.3 for equipment. 

(D) Outlet Devices. The rating or setting shall not exceed 
that specified in 210.21 for outlet devices. 

210.21 Outlet Devices. Outlet devices shall have an am- 
pere rating that is not less than the load to be served and 
shall comply with 210.21(A) and (B). 



NATIONAL ELECTRICAL CODE 



2002 Edition 



70-56 



ARTICLE 210 — BRANCH CIRCUITS 



(A) Lampholders. Where connected to a branch circuit 
having a rating in excess of 20 amperes, lampholders shall 
be of the heavy-duty type. A heavy-duty lampholder shall 
have a rating of not less than 660 watts if of the admedium 
type and not less than 750 watts if of any other type. 

(B) Receptacles. 

(1) Single Receptacle on an Individual Branch Circuit. 

A single receptacle installed on an individual branch circuit 
shall have an ampere rating not less than that of the branch 
circuit. 

Exception No. 1: A receptacle installed in accordance with 
430.81(C). 

Exception No. 2: A receptacle installed exclusively for the 
use of a cord-and-plug-connected arc welder shall be per- 
mitted to have an ampere rating not less than the minimum 
branch-circuit conductor ampacity determined by 
630.11(A) for arc welders. 

FPN: See definition of receptacle in Article 100. 

(2) Total Cord-and-Plug-Connected Load. Where con- 
nected to a branch circuit supplying two or more recep- 
tacles or outlets, a receptacle shall not supply a total cord- 
and-plug-connected load in excess of the maximum 
specified in Table 210.21(B)(2). 

Table 210.21(B)(2) Maximum Cord-and-Plug-Connected 
Load to Receptacle 



Circuit Rating 
(Amperes) 



Receptacle Rating 
(Amperes) 



Maximum Load 
(Amperes) 



15 or 20 
20 
30 



15 
20 
30 



12 
16 

24 



(3) Receptacle Ratings. Where connected to a branch cir- 
cuit supplying two or more receptacles or outlets, recep- 
tacle ratings shall conform to the values listed in Table 
210.21(B)(3), or where larger than 50 amperes, the recep- 
tacle rating shall not be less than the branch-circuit rating. 

Exception No. 1: Receptacles for one or more cord-and- 
plug-connected arc welders shall be permitted to have am- 
pere ratings not less than the minimum branch-circuit con- 
ductor ampacity permitted by 630.11(A) or (B) as 
applicable for arc welders. 

Exception No. 2: The ampere rating of a receptacle in- 
stalled for electric discharge lighting shall be permitted to 
be based on 410.30(C). 

(4) Range Receptacle Rating. The ampere rating of a 
range receptacle shall be permitted to be based on a single 
range demand load as specified in Table 220.19. 



Table 210.21(B)(3) Receptacle Ratings for Various Size 
Circuits 



Circuit Rating (Amperes) Receptacle Rating (Amperes) 



15 
20 
30 
40 
50 



Not over 15 
15 or 20 

30 

40 or 50 

50 



210.23 Permissible Loads. In no case shall the load ex- 
ceed the branch-circuit ampere rating. An individual branch 
circuit shall be permitted to supply any load for which it is 
rated. A branch circuit supplying two or more outlets or 
receptacles shall supply only the loads specified according 
to its size as specified in 210.23(A) through (D) and as 
summarized in 210.24 and Table 210.24. 

(A) 15- and 20- Ampere Branch Circuits. A 15- or 20- 

ampere branch circuit shall be permitted to supply lighting 
units or other utilization equipment, or a combination of 
both, and shall comply with 210.23(A)(1) and (A)(2). 

Exception: The small appliance branch circuits, laundry 
branch circuits, and bathroom branch circuits required in a 
dwelling unit(s) by 210.11(C)(1), (2), and (3) shall supply 
only the receptacle outlets specified in that section. 

(1) Cord-and-Plug-Connected Equipment. The rating of 
any one cord-and-plug-connected utilization equipment 
shall not exceed 80 percent of the branch-circuit ampere 
rating. 

(2) Utilization Equipment Fastened in Place. The total 
rating of utilization equipment fastened in place, other than 
luminaires (lighting fixtures), shall not exceed 50 percent of 
the branch-circuit ampere rating where lighting units, cord- 
and-plug-connected utilization equipment not fastened in 
place, or both, are also supplied. 

(B) 30-Ampere Branch Circuits. A 30-ampere branch cir- 
cuit shall be permitted to supply fixed lighting units with 
heavy-duty lampholders in other than a dwelling unit(s) or 
utilization equipment in any occupancy. A rating of any one 
cord-and-plug-connected utilization equipment, shall not 
exceed 80 percent of the branch-circuit ampere rating. 

(C) 40- and 50-Ampere Branch Circuits. A 40- or 50- 

ampere branch circuit shall be permitted to supply cooking 
appliances that are fastened in place in any occupancy. In 
other than dwelling units, such circuits shall be permitted to 
supply fixed lighting units with heavy-duty lampholders, 
infrared heating units, or other utilization equipment. 

(D) Branch Circuits Larger Than 50 Amperes. Branch 
circuits larger than 50 amperes shall supply only nonlight- 
ing outlet loads. 



• 



2002 Edition 



NATIONAL ELECTRICAL CODE 



ARTICLE 210 — BRANCH CIRCUITS 



70-57 



210.24 Branch-Circuit Requirements — Summary. The 

requirements for circuits that have two or more outlets or 
receptacles, other than the receptacle circuits of 
210.11(C)(1) and (2), are summarized in Table 210.24. This 
table provides only a summary of minimum requirements. 
See 210.19, 210.20, and 210.21 for the specific require- 
ments applying to branch circuits. 

210.25 Common Area Branch Circuits. Branch circuits 
in dwelling units shall supply only loads within that dwell- 
ing unit or loads associated only with that dwelling unit. 
Branch circuits required for the purpose of lighting, central 
alarm, signal, communications, or other needs for public or 
common areas of a two-family or multifamily dwelling 
shall not be supplied from equipment that supplies an indi- 
vidual dwelling unit. 

III. Required Outlets 

210.50 General. Receptacle outlets shall be installed as 
specified in 210.52 through 210.63. 

(A) Cord Pendants. A cord connector that is supplied by a 
permanently connected cord pendant shall be considered a 
receptacle outlet. 

(B) Cord Connections. A receptacle outlet shall be in- 
stalled wherever flexible cords with attachment plugs are 
used. Where flexible cords are permitted to be permanently 
connected, receptacles shall be permitted to be omitted for 
such cords. 

(C) Appliance Outlets. Appliance receptacle outlets in- 
stalled in a dwelling unit for specific appliances, such as 
laundry equipment, shall be installed within 1.8 m (6 ft) of 
the intended location of the appliance. 



210.52 Dwelling Unit Receptacle Outlets. This section 
provides requirements for 125-volt, 15- and 20-ampere re- 
ceptacle outlets. Receptacle outlets required by this section 
shall be in addition to any receptacle that is part of a lumi- 
naire (lighting fixture) or appliance, located within cabinets 
or cupboards, or located more than 1.7 m (5 J /2 ft) above the 
floor. 

Permanently installed electric baseboard heaters 
equipped with factory-installed receptacle outlets or outlets 
provided as a separate assembly by the manufacturer shall 
be permitted as the required outlet or outlets for the wall 
space utilized by such permanently installed heaters. Such 
receptacle outlets shall not be connected to the heater cir- 
cuits. 

FPN: Listed baseboard heaters include instructions that 
may not permit their installation below receptacle outlets. 

(A) General Provisions. In every kitchen, family room, 
dining room, living room, parlor, library, den, sunroom, 
bedroom, recreation room, or similar room or area of 
dwelling units, receptacle outlets shall be installed in accor- 
dance with the general provisions specified in 210.52(A)(1) 
through (A)(3). 

(1) Spacing. Receptacles shall be installed so that no point 
measured horizontally along the floor line in any wall space 
is more than 1.8 m (6 ft) from a receptacle outlet. 

(2) Wall Space. As used in this section, a wall space shall 
include the following: 

(1) Any space 600 mm (2 ft) or more in width (including 
space measured around corners) and unbroken along 
the floor line by doorways, fireplaces, and similar open- 
ings 

(2) The space occupied by fixed panels in exterior walls, 
excluding sliding panels 



Table 210.24 Summary of Branch-Circuit Requirements 



Circuit Rating 



15 A 



20 A 



30 A 



40 A 



50 A 



Conductors (min. size): 








Circuit wires 1 


14 


12 


10 


Taps 


14 


14 


14 


Fixture wires and cords — See 240.5 









12 



'These gauges are for copper conductors. 

2 For receptacle rating of cord-connected electric-discharge luminaires (lighting fixtures), see 410.30(C). 



6 

12 



Overcurrent Protection 


15 A 


20 A 


30 A 


40 A 


50 A 


Outlet devices: 
Lampholders permitted 
Receptacle rating 2 


Any type 
15 max. A 


Any type 
15 or 20 A 


Heavy duty 
30 A 


Heavy duty 
40 or 50 A 


Heavy duty 
50 A 


Maximum Load 


15 A 


20 A 


30 A 


40 A 


50 A 


Permissible load 


See 210.23(A) 


See 210.23(A) 


See 210.23(B) 


See 210.23(C) 


See 210.23(C) 



NATIONAL ELECTRICAL CODE 



2002 Edition 



70-58 



ARTICLE 210 — BRANCH CIRCUITS 



(3) The space afforded by fixed room dividers such as free- 
standing bar-type counters or railings 

(3) Floor Receptacles. Receptacle outlets in floors shall 
not be counted as part of the required number of receptacle 
outlets unless located within 450 mm (18 in.) of the wall. 

(B) Small Appliances. 

(1) Receptacle Outlets Served. In the kitchen, pantry, 
breakfast room, dining room, or similar area of a dwelling 
unit, the two or more 20-ampere small-appliance branch 
circuits required by 210.11(C)(1) shall serve all receptacle 
outlets covered by 210.52(A) and (C) and receptacle outlets 
for refrigeration equipment. 

Exception No. 1: In addition to the required receptacles 
specified by 210.52, switched receptacles supplied from a 
general-purpose branch circuit as defined in 210.70(A)(1), 
Exception No. 1, shall be permitted. 

Exception No. 2: The receptacle outlet for refrigeration 
equipment shall be permitted to be supplied from an indi- 
vidual branch circuit rated 15 amperes or greater. 

(2) No Other Outlets. The two or more small-appliance 
branch circuits specified in 210.52(B)(1) shall have no 
other outlets. 

Exception No. 1: A receptacle installed solely for the elec- 
trical supply to and support of an electric clock in any of 
the rooms specified in 210.52(B)(1). 

Exception No. 2: Receptacles installed to provide power 
for supplemental equipment and lighting on gas-fired 
ranges, ovens, or counter-mounted cooking units. 

(3) Kitchen Receptacle Requirements. Receptacles in- 
stalled in a kitchen to serve countertop surfaces shall be 
supplied by not fewer than two small-appliance branch cir- 
cuits, either or both of which shall also be permitted to 
supply receptacle outlets in the same kitchen and in other 
rooms specified in 210.52(B)(1). Additional small-appliance 
branch circuits shall be permitted to supply receptacle outlets 
in the kitchen and other rooms specified in 210.52(B)(1). No 
small-appliance branch circuit shall serve more than one 
kitchen. 

(C) Countertops. In kitchens and dining rooms of dwell- 
ing units, receptacle outlets for counter spaces shall be in- 
stalled in accordance with 210.52(C)(1) through (5). 

(1) Wall Counter Spaces. A receptacle outlet shall be in- 
stalled at each wall counter space that is 300 mm (12 in.) or 
wider. Receptacle outlets shall be installed so that no point 
along the wall line is more than 600 mm (24 in.) measured 
horizontally from a receptacle outlet in that space. 

(2) Island Counter Spaces. At least one receptacle outlet 
shall be installed at each island counter space with a long 



dimension of 600 mm (24 in.) or greater and a short dimen- 
sion of 300 mm (12 in.) or greater. 

(3) Peninsular Counter Spaces. At least one receptacle 
outlet shall be installed at each peninsular counter space 
with a long dimension of 600 mm (24 in.) or greater and a 
short dimension of 300 mm (12 in.) or greater. A peninsular 
countertop is measured from the connecting edge. 

(4) Separate Spaces. Countertop spaces separated by 
range tops, refrigerators, or sinks shall be considered as 
separate countertop spaces in applying the requirements of 
210.52(C)(1), (2), and (3). 

(5) Receptacle Outlet Location. Receptacle outlets shall 
be located above, but not more than 500 mm (20 in.) above, 
the countertop. Receptacle outlets rendered not readily ac- 
cessible by appliances fastened in place, appliance garages, 
or appliances occupying dedicated space shall not be con- 
sidered as these required outlets. 

Exception: To comply with the conditions specified in (a) 
or (b), receptacle outlets shall be permitted to be mounted 
not more than 300 mm (12 in.) below the countertop. Re- 
ceptacles mounted below a countertop in accordance with 
this exception shall not be located where the countertop 
extends more than 150 mm (6 in.) beyond its support base. 

(a) Construction for the physically impaired. 

(b) On island and peninsular countertops where the coun- 
tertop is flat across its entire surface (no backsplashes, 
dividers, etc.) and there are no means to mount a re- 
ceptacle within 500 mm (20 in.) above the countertop, 
such as an overhead cabinet. 

(D) Bathrooms. In dwelling units, at least one wall recep- 
tacle outlet shall be installed in bathrooms within 900 mm 
(3 ft) of the outside edge of each basin. The receptacle 
outlet shall be located on a wall or partition that is adjacent 
to the basin or basin countertop. 

(E) Outdoor Outlets. For a one-family dwelling and each 
unit of a two-family dwelling that is at grade level, at least 
one receptacle outlet accessible at grade level and not more 
than 2.0 m (6'/2 ft) above grade shall be installed at the 
front and back of the dwelling. See 210.8(A)(3). 

(F) Laundry Areas. In dwelling units, at least one recep- 
tacle outlet shall be installed for the laundry. 

Exception No. 1: In a dwelling unit that is an apartment or 
living area in a multifamily building where laundry facili- 
ties are provided on the premises and are available to all 
building occupants, a laundry receptacle shall not be 
required. 

Exception No. 2: In other than one-family dwellings where 
laundry facilities are not to be installed or permitted, a 
laundry receptacle shall not be required. 



2002 Edition 



NATIONAL ELECTRICAL CODE 



ARTICLE 210 — BRANCH CIRCUITS 



70-59 



(G) Basements and Garages. For a one-family dwelling, 
at least one receptacle outlet, in addition to any provided 
for laundry equipment, shall be installed in each basement 
and in each attached garage, and in each detached garage 
with electric power. See 210.8(A)(2) and (A)(5). Where a 
portion of the basement is finished into one or more habit- 
able rooms, each separate unfinished portion shall have a 
receptacle outlet installed in accordance with this section. 

(H) Hallways. In dwelling units, hallways of 3.0 m (10 ft) 
or more in length shall have at least one receptacle outlet. 
As used in this subsection, the hall length shall be con- 
sidered the length along the centerline of the hall without 
passing through a doorway. 

210.60 Guest Rooms. 

(A) General. Guest rooms in hotels, motels, and similar 
occupancies shall have receptacle outlets installed in accor- 
dance with 210.52(A) and 210.52(D). Guest rooms meeting 
the definition of a dwelling unit shall have receptacle out- 
lets installed in accordance with all of the applicable rules 
in 210.52. 

(B) Receptacle Placement. In applying the provisions of 
210.52(A), the total number of receptacle outlets shall not 
be less than the minimum number that would comply with 
the provisions of that section. These receptacle outlets shall 
be permitted to be located conveniently for permanent fur- 
niture layout. At least two receptacle outlets shall be readily 
accessible. Where receptacles are installed behind the bed, 
the receptacle shall be located to prevent the bed from 
contacting any attachment plug that may be installed, or the 
receptacle shall be provided with a suitable guard. 

210.62 Show Windows. At least one receptacle outlet 
shall be installed directly above a show window for each 
3.7 linear m (12 ft) or major fraction thereof of show win- 
dow area measured horizontally at its maximum width. 

210.63 Heating, Air-Conditioning, and Refrigeration 
Equipment Outlet. A 125-volt, single-phase, 15- or 20- 
ampere-rated receptacle outlet shall be installed at an ac- 
cessible location for the servicing of heating, air- 
conditioning, and refrigeration equipment. The receptacle 
shall be located on the same level and within 7.5 m (25 ft) 
of the heating, air-conditioning, and refrigeration equip- 
ment. The receptacle outlet shall not be connected to the 
load side of the equipment disconnecting means. 

FPN: See 210.8 for ground-fault circuit-interrupter 
requirements. 

210.70 Lighting Outlets Required. Lighting outlets shall 
be installed where specified in 210.70(A), (B), and (C). 



(A) Dwelling Units. In dwelling units, lighting outlets 
shall be installed in accordance with 210.70(A)(1), (2), and 
(3). 

(1) Habitable Rooms. At least one wall switch-controlled 
lighting outlet shall be installed in every habitable room 
and bathroom. 

Exception No. 1: In other than kitchens and bathrooms, 
one or more receptacles controlled by a wall switch shall 
be permitted in lieu of lighting outlets. 

Exception No. 2: Lighting outlets shall be permitted to be 
controlled by occupancy sensors that are (1) in addition to 
wall switches or (2) located at a customary wall switch 
location and equipped with a manual override that will 
allow the sensor to function as a wall switch. 

(2) Additional Locations. Additional lighting outlets shall 
be installed in accordance with (a), (b), and (c). 

(a) At least one wall switch-controlled lighting outlet 
shall be installed in hallways, stairways, attached garages, 
and detached garages with electric power. 

(b) For dwelling units, attached garages, and detached 
garages with electric power, at least one wall switch- 
controlled lighting outlet shall be installed to provide illu- 
mination on the exterior side of outdoor entrances or exits 
with grade level access. A vehicle door in a garage shall not 
be considered as an outdoor entrance or exit. 

(c) Where one or more lighting outlet(s) are installed 
for interior stairways, there shall be a wall switch at each 
floor level, and landing level that includes an entry way, to 
control the lighting outlet(s) where the stairway between 
floor levels has six risers or more. 

Exception to (a), (b), and (c): In hallways, stairways, and 
at outdoor entrances, remote, central, or automatic control 
of lighting shall be permitted. 

(3) Storage or Equipment Spaces. For attics, underfloor 
spaces, utility rooms, and basements, at least one lighting 
outlet containing a switch or controlled by a wall switch 
shall be installed where these spaces are used for storage or 
contain equipment requiring servicing. At least one point of 
control shall be at the usual point of entry to these spaces. 
The lighting outlet shall be provided at or near the equip- 
ment requiring servicing. 

(B) Guest Rooms. At least one wall switch-controlled 
lighting outlet or wall switch-controlled receptacle shall be 
installed in guest rooms in hotels, motels, or similar occu- 
pancies. 

(C) Other Than Dwelling Units. For attics and underfloor 
spaces containing equipment requiring servicing, such as 
heating, air-conditioning, and refrigeration equipment, at 
least one lighting outlet containing a switch or controlled 



NATIONAL ELECTRICAL CODE 



2002 Edition 



70-60 



ARTICLE 215 — FEEDERS 



by a wall switch shall be installed in such spaces. At least 
one point of control shall be at the usual point of entry to 
these spaces. The lighting outlet shall be provided at or 
near the equipment requiring servicing. 



ARTICLE 215 
Feeders 



215.1 Scope. This article covers the installation require- 
ments, overcurrent protection requirements, minimum size, 
and ampacity of conductors for feeders supplying branch- 
circuit loads as computed in accordance with Article 220. 

Exception: Feeders for electrolytic cells as covered in 
668.3(C)(1) and (4). 

215.2 Minimum Rating and Size. 

(A) Feeders Not More Than 600 Volts. 

(1) General. Feeder conductors shall have an ampacity not 
less than required to supply the load as computed in Parts 
II, III, and IV of Article 220. The minimum feeder-circuit 
conductor size, before the application of any adjustment or 
correction factors, shall have an allowable ampacity not 
less than the noncontinuous load plus 125 percent of the 
continuous load. 

Exception: Where the assembly, including the overcurrent 
devices protecting the feeder(s), is listed for operation at 
100 percent of its rating, the allowable ampacity of the 
feeder conductors shall be permitted to be not less than the 
sum of the continuous load plus the noncontinuous load. 

Additional minimum sizes shall be as specified in (2), 
(3), and (4) under the conditions stipulated. 

(2) For Specified Circuits. The ampacity of feeder con- 
ductors shall not be less than 30 amperes where the load 
supplied consists of any of the following number and types 
of circuits: 

(1) Two or more 2- wire branch circuits supplied by a 
2-wire feeder 

(2) More than two 2-wire branch circuits supplied by a 
3 -wire feeder 

(3) Two or more 3-wire branch circuits supplied by a 
3-wire feeder 

(4) Two or more 4-wire branch circuits supplied by a 
3-phase, 4-wire feeder 

(3) Ampacity Relative to Service-Entrance Conductors. 

The feeder conductor ampacity shall not be less than that of 
the service-entrance conductors where the feeder conduc- 



tors cany the total load supplied by service-entrance con- 
ductors with an ampacity of 55 amperes or less. 

(4) Individual Dwelling Unit or Mobile Home Con- 
ductors.. Feeder conductors for individual dwelling units or 
mobile homes need not be larger than service-entrance con- 
ductors. Paragraph 310.15(B)(6) shall be permitted to be 
used for conductor size. 

FPN No. 1: See Examples Dl through D10 in Annex D. 

FPN No. 2: Conductors for feeders as defined in Article 
100, sized to prevent a voltage drop exceeding 3 percent at 
the farthest outlet of power, heating, and lighting loads, or 
combinations of such loads, and where the maximum total 
voltage drop on both feeders and branch circuits to the 
farthest outlet does not exceed 5 percent, will provide rea- 
sonable efficiency of operation. 

FPN No. 3: See 210.19(A), FPN No. 4, for voltage drop 
for branch circuits. 

(B) Feeders Over 600 Volts. The ampacity of conductors 
shall be in accordance with 310.15 and 310.60 as appli- 
cable. Feeder conductors over 600 volts shall be sized in 
accordance with 215.2(B)(1), (2), or (3). 

(1) Feeders Supplying Transformers. The ampacity of 
feeder conductors shall not be less than the sum of the 
nameplate ratings of the transformers supplied when only 
transformers are supplied. 

(2) Feeders Supplying Transformers and Utilization 
Equipment. The ampacity of feeders supplying a combina- 
tion of transformers and utilization equipment shall not be 
less than the sum of the nameplate ratings of the transform- 
ers and 125 percent of the designed potential load of the 
utilization equipment that will be operated simultaneously. 

(3) Supervised Installations. For supervised installations, 
feeder conductor sizing shall be permitted to be determined 
by qualified persons under engineering supervision. Super- 
vised installations are defined as those portions of a facility 
where all of the following conditions are met: 

(1) Conditions of design and installation are provided un- 
der engineering supervision. 

(2) Qualified persons with documented training and expe- 
rience in over 600-volt systems provide maintenance, 
monitoring, and servicing of the system. 

215.3 Overcurrent Protection. Feeders shall be protected 
against overcurrent in accordance with the provisions of 
Part I of Article 240. Where a feeder supplies continuous 
loads or any combination of continuous and noncontinuous 
loads, the rating of the overcurrent device shall not be less 
than the noncontinuous load plus 125 percent of the con- 
tinuous load. 



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Exception No. 1: Where the assembly, including the over- 
current devices protecting the feeder(s), is listed for opera- 
tion at 100 percent of its rating, the ampere rating of the 
overcurrent device shall be permitted to be not less than the 
sum of the continuous load plus the noncontinuous load. 

Exception No. 2: Overcurrent protection for feeders over 
600 volts, nominal, shall comply with Part IX of Article 240. 

215.4 Feeders with Common Neutral. 

(A) Feeders with Common Neutral. Two or three sets of 
3-wire feeders or two sets of 4-wire or 5-wire feeders shall 
be permitted to utilize a common neutral. 

(B) In Metal Raceway or Enclosure. Where installed in a 
metal raceway or other metal enclosure, all conductors of 
all feeders using a common neutral shall be enclosed within 
the same raceway or other enclosure as required in 300.20. 

215.5 Diagrams of Feeders. If required by the authority 
having jurisdiction, a diagram showing feeder details shall 
be provided prior to the installation of the feeders. Such a 
diagram shall show the area in square feet of the building 
or other structure supplied by each feeder, the total com- 
puted load before applying demand factors, the demand 
factors used, the computed load after applying demand fac- 
tors, and the size and type of conductors to be used. 

215.6 Feeder Conductor Grounding Means. Where a 
feeder supplies branch circuits in which equipment ground- 
ing conductors are required, the feeder shall include or pro- 
vide a grounding means, in accordance with the provisions 
of 250.134, to which the equipment grounding conductors 
of the branch circuits shall be connected. 

215.7 Ungrounded Conductors Tapped from Grounded 
Systems. Two-wire dc circuits and ac circuits of two or 
more ungrounded conductors shall be permitted to be 
tapped from the ungrounded conductors of circuits having a 
grounded neutral conductor. Switching devices in each tapped 
circuit shall have a pole in each ungrounded conductor. 

215.8 Means of Identifying Conductor with the Higher 
Voltage to Ground. On a 4-wire, delta-connected second- 
ary where the midpoint of one phase winding is grounded 
to supply lighting and similar loads, the phase conductor 
having the higher voltage to ground shall be identified by 
an outer finish that is orange in color or by tagging or other 
effective means. Such identification shall be placed at each 
point where a connection is made if the grounded conduc- 
tor is also present. 

215.9 Ground-Fault Circuit-Interrupter Protection for 
Personnel. Feeders supplying 15- and 20-ampere recep- 
tacle branch circuits shall be permitted to be protected by a 



ground-fault circuit interrupter in lieu of the provisions for 
such interrupters as specified in 210.8 and Article 527. 

215.10 Ground-Fault Protection of Equipment. Each 
feeder disconnect rated 1000 amperes or more and installed 
on solidly grounded wye electrical systems of more than 
150 volts to ground, but not exceeding 600 volts phase-to- 
phase, shall be provided with ground-fault protection of 
equipment in accordance with the provisions of 230.95. 

Exception No. 1: The provisions of this section shall not 
apply to a disconnecting means for a continuous industrial 
process where a nonorderly shutdown will introduce addi- 
tional or increased hazards. 

Exception No. 2: The provisions of this section shall not 
apply to fire pumps. 

Exception No. 3: The provisions of this section shall not 
apply if ground-fault protection of equipment is provided on 
the supply side of the feeder. 

215.11 Circuits Derived from Autotransformers. 

Feeders shall not be derived from autotransformers unless 
the system supplied has a grounded conductor that is elec- 
trically connected to a grounded conductor of the system 
supplying the autotransformer. 

Exception No. 1: An autotransformer shall be permitted 
without the connection to a grounded conductor where 
transforming from a nominal 208 volts to a nominal 240- 
volt supply or similarly from 240 volts to 208 volts. 

Exception No. 2: In industrial occupancies, where condi- 
tions of maintenance and supervision ensure that only 
qualified persons service the installation, autotransformers 
shall be permitted to supply nominal 600-volt loads from 
nominal 480-volt systems, and 480-volt loads from nominal 
600-volt systems, without the connection to a similar 
grounded conductor. 



ARTICLE 220 

Branch-Circuit, Feeder, and Service 

Calculations 

I. General 

220.1 Scope. This article provides requirements for com- 
puting branch-circuit, feeder, and service loads. 

Exception: Branch-circuit and feeder calculations for elec- 
trolytic cells as covered in 668.3(C)(1) and (4). 

220.2 Computations. 

(A) Voltages. Unless other voltages are specified, for pur- 
poses of computing branch-circuit and feeder loads, nomi- 



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nal system voltages of 120, 120/240, 208Y/120, 240, 347, 
480Y/277, 480, 600Y/347, and 600 volts shall be used. 

(B) Fractions of an Ampere. Where computations result 
in a fraction of an ampere that is less than 0.5, such frac- 
tions shall be permitted to be dropped. 

220.3 Computation of Branch Circuit Loads. Branch- 
circuit loads shall be computed as shown in 220.3(A) 
through (C). 

(A) Lighting Load for Specified Occupancies. A unit 
load of not less than that specified in Table 220.3(A) for 
occupancies specified therein shall constitute the minimum 
lighting load. The floor area for each floor shall be com- 
puted from the outside dimensions of the building, dwelling 
unit, or other area involved. For dwelling units, the com- 
puted floor area shall not include open porches, garages, or 
unused or unfinished spaces not adaptable for future use. 

FPN: The unit values herein are based on minimum load 
conditions and 100 percent power factor and may not pro- 
vide sufficient capacity for the installation contemplated. 

(B) Other Loads — All Occupancies. In all occupancies, 
the minimum load for each outlet for general-use recep- 
tacles and outlets not used for general illumination shall not 
be less than that computed in 220.3(B)(1) through (11), the 
loads shown being based on nominal branch-circuit volt- 
ages. 

Exception: The loads of outlets serving switchboards and 
switching frames in telephone exchanges shall be waived 
from the computations. 

(1) Specific Appliances or Loads. An outlet for a specific 
appliance or other load not covered in (2) through (11) shall 
be computed based on the ampere rating of the appliance or 
load served. 

(2) Electric Dryers and Household Electric Cooking 
Appliances. Load computations shall be permitted as 
specified in 220.18 for electric dryers and in 220.19 for 
electric ranges and other cooking appliances. 

(3) Motor Loads. Outlets for motor loads shall be com- 
puted in accordance with the requirements in 430.22, 
430.24, and 440.6. 

(4) Recessed Luminaires (Lighting Fixtures). An outlet 
supplying recessed luminaire(s) [lighting fixture(s)] shall be 
computed based on the maximum volt-ampere rating of the 
equipment and lamps for which the luminaire(s) [fixture(s)] 
is rated. 

(5) Heavy-Duty Lampholders. Outlets for heavy-duty 
lampholders shall be computed at a minimum of 600 volt- 
amperes. 



Table 220.3(A) General Lighting Loads by Occupancy 





Unit Load 




Volt-Amperes per 


Volt-Amperes per 


Type of Occupancy 


Square Meter 


Square Foot 


Armories and 


11 


1 


auditoriums 






Banks 


39 b 


3'/ 2 b 


Barber shops and 


33 


3 


beauty parlors 






Churches 


11 


1 


Clubs 


22 


2 


Court rooms 


22 


2 


Dwelling units 3 


33 


3 


Garages — 


6 


'/2 


commercial (storage) 






Hospitals 


22 


2 


Hotels and motels, 


22 


2 


including apartment 






houses without 






provision for 






cooking by tenants 3 






Industrial commercial 


22 


2 


(loft) buildings 






Lodge rooms 


17 


Wi 


Office buildings 


39 


3'/ 2 b 


Restaurants 


22 


2 


Schools 


33 


3 


Stores 


33 


3 


Warehouses (storage) 


3 


Va 


In any of the preceding 






occupancies except 






one-family dwellings 






and individual 






dwelling units of 






two-family and 






multifamily 






dwellings: 






Assembly halls 


11 


1 


and auditoriums 






Halls, corridors, 


6 


'/2 


closets, stairways 






Storage spaces 


3 


Va 



a See 220.3(B)(10). 

b In addition, a unit load of 11 volt-amperes/m 2 or 1 volt-ampere/ft 2 
shall be included for general-purpose receptacle outlets where the 
actual number of general -purpose receptacle outlets is unknown. 



(6) Sign and Outline Lighting. Sign and outline lighting 
outlets shall be computed at a minimum of 1200 volt- 
amperes for each required branch circuit specified in 
600.5(A). 

(7) Show Windows. Show windows shall be computed in 
accordance with either of the following: 

(1) The unit load per outlet as required in other provisions 
of this section 

(2) At 200 volt-amperes per 300 mm (1 ft) of show win- 
dow 



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• 



(8) Fixed Multioutlet Assemblies. Fixed multioutlet as- 
semblies used in other than dwelling units or the guest 
rooms of hotels or motels shall be computed in accordance 
with (1) or (2). For the purposes of this section, the com- 
putation shall be permitted to be based on the portion that 
contains receptacle outlets. 

(1) Where appliances are unlikely to be used simulta- 
neously, each 1.5 m (5 ft) or fraction thereof of each 
separate and continuous length shall be considered as 
one outlet of not less than 1 80 volt-amperes. 

(2) Where appliances are likely to be used simultaneously, 
each 300 mm (1 ft) or fraction thereof shall be consid- 
ered as an outlet of not less than 180 volt-amperes. 

(9) Receptacle Outlets. Except as covered in 220.3(B)(10), 
receptacle outlets shall be computed at not less than 180 
volt-amperes for each single or for each multiple receptacle 
on one yoke. A single piece of equipment consisting of a 
multiple receptacle comprised of four or more receptacles 
shall be computed at not less than 90 volt-amperes per 
receptacle. 

This provision shall not be applicable to the receptacle 
outlets specified in 210.11(C)(1) and (2). 

(10) Dwelling Occupancies. In one-family, two-family, 
and multifamily dwellings and in guest rooms of hotels and. 
motels, the outlets specified in (1), (2), and (3) are included 
in the general lighting load calculations of 220.3(A). No 
additional load calculations shall be required for such out- 
lets. 

(1) All general-use receptacle outlets of 20-ampere rating 
or less, including receptacles connected to the circuits 
in 210.11(C)(3) 

(2) The receptacle outlets specified in 210.52(E) and (G) 

(3) The lighting outlets specified in 210.70(A) and (B) 

(11) Other Outlets. Other outlets not covered in 
220.3(B)(1) through (10) shall be computed based on 180 
volt-amperes per outlet. 

(C) Loads for Additions to Existing Installations. 

(1) Dwelling Units. Loads added to an existing dwelling 
unit(s) shall comply with the following as applicable: 

(1) Loads for structural additions to an existing dwelling 
unit or for a previously unwired portion of an existing 
dwelling unit, either of which exceeds 46.5 m 2 



puted in accordance with either 220.3(A) or (B), as appli- 
cable. 

220.4 Maximum Loads. The total load shall not exceed 
the rating of the branch circuit, and it shall not exceed the 
maximum loads specified in 220.4(A) through (C) under 
the conditions specified therein. 

(A) Motor-Operated and Combination Loads. Where a 
circuit supplies only motor-operated loads, Article 430 shall 
apply. Where a circuit supplies only air-conditioning equip- 
ment, refrigerating equipment, or both, Article 440 shall 
apply. For circuits supplying loads consisting of motor- 
operated utilization equipment that is fastened in place and 
has a motor larger than Vs hp in combination with other 
loads, the total computed load shall be based on 125 per- 
cent of the largest motor load plus the sum of the other 
loads. 

(B) Inductive Lighting Loads. For circuits supplying 
lighting units that have ballasts, transformers, or autotrans- 
formers, the computed load shall be based on the total am- 
pere ratings of such units and not on the total watts of the 
lamps. 

(C) Range Loads. It shall be permissible to apply demand 
factors for range loads in accordance with Table 220.19, 
including Note 4. 

II. Feeders and Services 

220.10 General. The computed load of a feeder or service 
shall not be less than the sum of the loads on the branch 
circuits supplied, as determined by Part I of this article, 
after any applicable demand factors permitted by Parts II, 

III, or IV have been applied. 

FPN: See Examples D1(A) through D10 in Annex D. See 
220.4(B) for the maximum load in amperes permitted for 
lighting units operating at less than 100 percent power 
factor. 

220.11 General Lighting. The demand factors specified in 
Table 220. 1 1 shall apply to that portion of the total branch- 
circuit load computed for general illumination. They shall 
not be applied in determining the number of branch circuits 
for general illumination. 



(500 ft 2 ), shall be computed in accordance with 22012 Show- Window and Track Lighting. 



220.3(A) and (B). 
(2) Loads for new circuits or extended circuits in previ- 
ously wired dwelling units shall be computed in accor- 
dance with either 220.3(A) or (B), as applicable. 

(2) Other Than Dwelling Units. Loads for new circuits or 
extended circuits in other than dwelling units shall be com- 



(A) Show Windows. For show-window lighting, a load of 
not less than 660 volt-amperes/linear meter or 200 volt- 
amperes/linear foot shall be included for a show window, 
measured horizontally along its base. 

FPN: See 220.3(B)(7) for branch circuits supplying show 
windows. 



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ARTICLE 220 — BRANCH-CIRCUIT, FEEDER, AND SERVICE CALCULATIONS 



Table 220.11 Lighting Load Demand Factors 





Portion of Lighting Load 


Demand 


Type of 


to Which Demand Factor 


Factor 


Occupancy 


Applies (Volt-Amperes) 


(Percent) 


Dwelling units 


First 3000 or less at 


100 




From 3001 to 120,000 at 


35 




Remainder over 120,000 at 


25 


Hospitals* 


First 50,000 or less at 


40 




Remainder over 50,000 at 


20 


Hotels and motels, 


First 20,000 or less at 


50 


including 


From 20,001 to 100,000 at 


40 


apartment houses 


Remainder over 100,000 at 


30 


without provision 






for cooking by 






tenants* 






Warehouses 


First 12,500 or less at 


100 


(storage) 


Remainder over 12,500 at 


50 


All others 


Total volt-amperes 


100 



*The demand factors of this table shall not apply to the computed load 
of feeders or services supplying areas in hospitals, hotels, and motels 
where the entire lighting is likely to be used at one time, as in oper- 
ating rooms, ballrooms, or dining rooms. 



(B) Track Lighting. For track lighting in other than dwell- 
ing units or guest rooms of hotels or motels, an additional 
load of 150 volt-amperes shall be included for every 
600 mm (2 ft) of lighting track or fraction thereof. Where 
multicircuit track is installed, the load shall be considered 
to be divided equally between the track circuits. 

220.13 Receptacle Loads — Nond welling Units. In other 
than dwelling units, receptacle loads computed at not more 
than 180 volt-amperes per outlet in accordance with 
220.3(B)(9) and fixed multioutlet assemblies computed in 
accordance with 220.3(B)(8) shall be permitted to be added 
to the lighting loads and made subject to the demand fac- 
tors given in Table 220. 1 1 , or they shall be permitted to be 
made subject to the demand factors given in Table 220.13. 

Table 220.13 Demand Factors for Nond welling Receptacle 
Loads 

Portion of Receptacle Load to Which 

Demand Factor Applies Demand Factor 

(Volt-Amperes) (Percent) 



First 10 kVA or less at 
.Remainder over 10 kVA at 



100 
50 



220.14 Motors. Motor loads shall be computed in accor- 
dance with 430.24, 430.25, and 430.26 and with 440.6 for 
hermetic refrigerant motor compressors. 



220.15 Fixed Electric Space Heating. Fixed electric 
space heating loads shall be computed at 100 percent of the 
total connected load; however, in no case shall a feeder or 
service load current rating be less than the rating of the 
largest branch circuit supplied. 

Exception: Where reduced loading of the conductors re- 
sults from units operating on duty-cycle, intermittently, or 
from all units not operating at the same time, the authority 
having jurisdiction may grant permission for feeder and 
service conductors to have an ampacity less than 100 per- 
cent, provided the conductors have an ampacity for the 
load so determined. 

220.16 Small Appliance and Laundry Loads — 
Dwelling Unit. 

(A) Small Appliance Circuit Load. In each dwelling unit, 
the load shall be computed at 1500 volt-amperes for each 
2-wire small-appliance branch circuit required by 
210.11(C)(1). Where the load is subdivided through two or 
more feeders, the computed load for each shall include not 
less than 1500 volt-amperes for each 2-wire small- 
appliance branch circuit. These loads shall be permitted to 
be included with the general lighting load and subjected to 
the demand factors provided in Table 220.11. 

Exception: The individual branch circuit permitted by 
210.52(B)(1), Exception No. 2, shall be permitted to be 
excluded from the calculation required by 220.16. 

(B) Laundry Circuit Load. A load of not less than 1500 
volt-amperes shall be included for each 2-wire laundry 
branch circuit installed as required by 210.11(C)(2). This 
load shall be permitted to be included with the general 
lighting load and subjected to the demand factors provided 
in Table 220.11. 

220.17 Appliance Load — Dwelling Unit(s). It shall be 
permissible to apply a demand factor of 75 percent to the 
nameplate rating load of four or more appliances fastened 
in place, other than electric ranges, clothes dryers, space- 
heating equipment, or air-conditioning equipment, that are 
served by the same feeder or service in a one-family, two- 
family, or multifamily dwelling. 

220.18 Electric Clothes Dryers — Dwelling Unit(s). The 

load for household electric clothes dryers in a dwelling 
unit(s) shall be 5000 watts (volt-amperes) or the nameplate 
rating, whichever is larger, for each dryer served. The use 
of the demand factors in Table 220.18 shall be permitted. 
Where two or more single-phase dryers are supplied by a 
3-phase, 4-wire feeder or service, the total load shall be 
computed on the basis of twice the maximum number con- 
nected between any two phases. 



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ARTICLE 220 — BRANCH-CIRCUIT, FEEDER, AND SERVICE CALCULATIONS 



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Table 220.18 Demand Factors for Household Electric 
Clothes Dryers 



Number of Dryers 



Demand Factor (Percent) 



1-4 
5 
6 

7 



9 
10 
11 

12-22 



100% 

85% 
75% 
65% 

60% 
55% 
50% 
47% 
% = 47 - (number of dryers - 11) 



23 




35% 


24-^2 


% = 35 - 


- [0.5 x (number of dryers - 
23)] 


43 and over 




25% 



220.19 Electric Ranges and Other Cooking Appliances 
— Dwelling Unit(s). The demand load for household 
electric ranges, wall-mounted ovens, counter-mounted 
cooking units, and other household cooking appli- 
ances individually rated in excess of VA kW shall be per- 
mitted to be computed in accordance with Table 220.19. 
Kilovolt-amperes (kVA) shall be considered equivalent to 



Table 220.19 Demand Loads for Household Electric Ranges, 
Wall-Mounted Ovens, Counter-Mounted Cooking Units, and 
Other Household Cooking Appliances over 1% kW Rating 
(Column C to be used in all cases except as otherwise 
permitted in Note 3.) 





Demand Factor (Percent) 






(See 


Notes) 


Column C 
Maximum 










Column A 


Column B 


Demand (kW) 




(Less than 


(3V 2 kW to 


(See Notes) 


Number of 


Vh kW 


8% kW 


(Not over 12 


Appliances 


Rating) 


Rating) 


kW Rating) 


1 


80 


80 


8 


2 


75 


65 


11 


3 


70 


55 


14 


4 


66 


50 


17 


5 


62 


45 


20 


6 


59 


43 


21 


7 


56 


40 


22 


8 


53 


36 


23 


9 


51 


35 


24 


10 


49 


34 


25 


11 


47 


32 


26 


12 


45 


32 


27 


13 


43 


32 


28 



Table 220.19 Continued 





Demand Factor (Percent) 






(See Notes) 


Column C 








Maximum 




Column A 


Column B 


Demand (kW) 




(Less than 


(3Vi kW to 


(See Notes) 


Number of 


3Yz kW 


8% kW 


(Not over 12 


Appliances 


Rating) 


Rating) 


kW Rating) 


14 


41 


32 


29 


15 


40 


32 


30 


16 


39 


28 


31 


17 


38 


28 


32 


18 


37 


28 


33 


19 


36 


28 


34 


20 


35 


28 


35 


21 


34 


26 


36 


22 


33 


26 


37 


23 


32 


26 


38 


24 


31 


26 


39 


25 


30 


26 


40 


26-30 


30 


24 


15 kW + 1 kW 


31-40 


30 


22 


for each range 


41-50 


30 


20 


25 kW + 3/ 4 kW 


51-60 


30 


18 


for each range 


61 and over 


30 


16 





1. Over 12 kW through 27 kW ranges all of same rating. For ranges 
individually rated more than 12 kW but not more than 27 kW, the 
maximum demand in Column C shall be increased 5 percent for each 
additional kilowatt of rating or major fraction thereof by which the 
rating of individual ranges exceeds 12 kW. 

2. Over 8% kW through 27 kW ranges of unequal ratings. For ranges 
individually rated more than 8% kW and of different ratings, but none 
exceeding 27 kW, an average value of rating shall be computed by 
adding together the ratings of all ranges to obtain the total connected 
load (using 12 kW for any range rated less than 12 kW) and dividing 
by the total number of ranges. Then the maximum demand in Column 
C shall be increased 5 percent for each kilowatt or major fraction 
thereof by which this average value exceeds 12 kW. 

3. Over 1% kW through 8% kW. In lieu of the method provided in 
Column C, it shall be permissible to add the nameplate ratings of all 
household cooking appliances rated more than 1% kW but not more 
than 8% kW and multiply the sum by the demand factors specified in 
Column A or B for the given number of appliances. Where the rating 
of cooking appliances falls under both Column A and Column B, the 
demand factors for each column shall be applied to the appliances for 
that column, and the results added together. 

4. Branch-Circuit Load. It shall be permissible to compute the branch- 
circuit load for one range in accordance with Table 220.19. The 
branch-circuit load for one wall-mounted oven or one counter- 
mounted cooking unit shall be the nameplate rating of the appliance. 
The branch-circuit load for a counter-mounted cooking unit and not 
more than two wall-mounted ovens, all supplied from a single branch 
circuit and located in the same room, shall be computed by adding the 
nameplate rating of the individual appliances and treating this total as 
equivalent to one range. 

5. This table also applies to household cooking appliances rated over 
PA kW and used in instructional programs. 



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kilowatts (kW) for loads computed under this section. 

Where two or more single-phase ranges are supplied by 
a 3-phase, 4-wire feeder or service, the total load shall be 
computed on the basis of twice the maximum number con- 
nected between any two phases. 

FPN No. 1: See Example D5(A) in Annex D. 

FPN No. 2: See Table 220.20 for commercial cooking 
equipment. 

FPN No. 3: See the examples in Annex D. 

220.20 Kitchen Equipment — Other Than Dwelling 
Unit(s). It shall be permissible to compute the load for 
commercial electric cooking equipment, dishwasher 
booster heaters, water heaters, and other kitchen equipment 
in accordance with Table 220.20. These demand factors 
shall be applied to all equipment that has either thermo- 
static control or intermittent use as kitchen equipment. 
They shall not apply to space-heating, ventilating, or air- 
conditioning equipment. 

However, in no case shall the feeder or service demand 
be less than the sum of the largest two kitchen equipment 
loads. 

Table 220.20 Demand Factors for Kitchen Equipment — 
Other Than Dwelling Unit(s) 



Number of Units of 
Equipment 



Demand Factor (Percent) 



1 
2 
3 
4 
5 
6 and over 



100 
100 
90 
80 
70 
65 



220.21 Noncoincident Loads. Where it is unlikely that 
two or more noncoincident loads will be in use simulta- 
neously, it shall be permissible to use only the largest 
load(s) that will be used at one time, in computing the total 
load of a feeder or service. 

220.22 Feeder or Service Neutral Load. The feeder or 
service neutral load shall be the maximum unbalance of the 
load determined by this article. The maximum unbalanced 
load shall be the maximum net computed load between the 
neutral and any one ungrounded conductor, except that the 
load thus obtained shall be multiplied by 140 percent for 
3-wire, 2-phase or 5-wire, 2-phase systems. For a feeder or 
service supplying household electric ranges, wall-mounted 
ovens, counter-mounted cooking units, and electric dryers, 
the maximum unbalanced load shall be considered as 
70 percent of the load on the ungrounded conductors, as 
determined in accordance with Table 220.19 for ranges and 



Table 220.18 for dryers. For 3-wire dc or single-phase ac; 
4-wire, 3-phase; 3-wire, 2-phase; or 5-wire, 2-phase sys- 
tems, a further demand factor of 70 percent shall be per- 
mitted for that portion of the unbalanced load in excess of 
200 amperes. There shall be no reduction of the neutral 
capacity for that portion of the load that consists of nonlin- 
ear loads supplied from a 4-wire, wye-connected, 3-phase 
system. There shall be no reduction in the capacity of the 
grounded conductor of a 3-wire circuit consisting of two 
phase wires and the neutral of a 4-wire, 3-phase, wye- 
connected system. 

FPN No. 1: See Examples D1(A), D1(B), D2(B), D4(A), 
and D5(A) in Annex D. 

FPN No. 2: A 3-phase, 4-wire, wye-connected power sys- 
tem used to supply power to nonlinear loads may necessi- 
tate that the power system design allow for the possibility 
of high harmonic neutral currents. 

III. Optional Calculations for Computing Feeder and 
Service Loads 

220.30 Optional Calculation — Dwelling Unit. 

(A) Feeder and Service Load. For a dwelling unit having 
the total connected load served by a single 3-wire, 120/240- 
volt or 208Y/120-volt set of service or feeder conductors 
with an ampacity of 100 or greater, it shall be permissible 
to compute the feeder and service loads in accordance with 
this section instead of the method specified in Part II of this 
article. The calculated load shall be the result of adding the 
loads from 220.30(B) and (C). Feeder and service-entrance 
conductors whose demand load is determined by this op- 
tional calculation shall be permitted to have the neutral load 
determined by 220.22. 

(B) General Loads. The general calculated load shall be 
not less than 100 percent of the first 10 kVA plus 40 percent 
of the remainder of the following loads: 

(1) 1500 volt- amperes for each 2- wire, 20-ampere small- 
appliance branch circuit and each laundry branch cir- 
cuit specified in 220.16. 

(2) 33 volt-amperes/m 2 or 3 volt-amperes/ft 2 for general 
lighting and general-use receptacles. The floor area for 
each floor shall be computed from the outside dimen- 
sions of the dwelling unit. The computed floor area 
shall not include open porches, garages, or unused or 
unfinished spaces not adaptable for future use. 

(3) The nameplate rating of all appliances that are fastened 
in place, permanently connected, or located to be on a 
specific circuit, ranges, wall-mounted ovens, counter- 
mounted cooking units, clothes dryers, and water heat- 
ers. 

(4) The nameplate ampere or kVA rating of all motors and 
of all low-power-factor loads. 



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(C) Heating and Air-Conditioning Load. The largest of 
the following six selections (load in kVA) shall be in- 
cluded: 

(1) 100 percent of the nameplate rating(s) of the air condi- 
tioning and cooling. 

(2) 100 percent of the nameplate ratings of the heat pump 
compressors and supplemental heating unless the con- 
troller prevents the compressor and supplemental heat- 
ing from operating at the same time. 

(3) 100 percent of the nameplate ratings of electric thermal 
storage and other heating systems where the usual load 
is expected to be continuous at the full nameplate 
value. Systems qualifying under this selection shall not 
be calculated under any other selection in 220.30(C). 

(4) 65 percent of the nameplate rating(s) of the central 
electric space heating, including integral supplemental 
heating in heat pumps where the controller prevents the 
compressor and supplemental heating from operating at 
the same time. 

(5) 65 percent of the nameplate rating(s) of electric space 
heating if less than four separately controlled units. 

(6) 40 percent of the nameplate rating(s) of electric space 
heating if four or more separately controlled units. 

220.31 Optional Calculations for Additional Loads in 
an Existing Dwelling Unit. This section shall be permitted 
to be used to determine if the existing service or feeder is of 
sufficient capacity to serve additional loads. Where the 
dwelling unit is served by a 120/240-volt or 208 Y/l 20- volt, 
3-wire service, it shall be permissible to compute the total 
load in accordance with 220.31(A) or (B). 

(A) Where Additional Air-Conditioning Equipment or 
Electric Space-Heating Equipment Is Not to Be 
Installed. The following formula shall be used for existing 
and additional new loads. 



Load (kVa) 



Percent of Load 



First 8 kVA of load at 
Remainder of load at 



100 
40 



Load calculations shall include the following: 

(1) General lighting and general-use receptacles at 33 volt- 
amperes/m 2 or 3 volt-amperes/ft 2 as determined by 
220.3(A) 

(2) 1500 volt-amperes for each 2- wire, 20-ampere small- 
appliance branch circuit and each laundry branch cir- 
cuit specified in 220.16 

(3) Household range(s), wall-mounted oven(s), and 
counter-mounted cooking unit(s) 

(4) All other appliances that are permanently connected, 
fastened in place, or connected to a dedicated circuit, at 
nameplate rating 



(B) Where Additional Air-Conditioning Equipment or 
Electric Space-Heating Equipment Is to Be Installed. 

The following formula shall be used for existing and addi- 
tional new loads. The larger connected load of air- 
conditioning or space-heating, but not both, shall be used. 

Air-conditioning equipment 100 

Central electric space heating 100 

Less than four separately 100 

controlled space-heating units 

First 8 kVA of all other loads 100 

Remainder of all other loads 40 

Other loads shall include the following: 

(1) General lighting and general-use receptacles at 33 volt- 
amperes/m 2 or 3 volt-amperes/ft 2 as determined by 
220.3(A) 

(2) 1500 volt-amperes for each 2- wire, 20-ampere small- 
appliance branch circuit and each laundry branch cir- 
cuit specified in 220.16 

(3) Household range(s), wall-mounted oven(s), and 
counter-mounted cooking unit(s) 

(4) All other appliances that are permanently connected, 
fastened in place, or connected to a dedicated circuit, 
including four or more separately controlled space- 
heating units, at nameplate rating 

220.32 Optional Calculation — Multifamily Dwelling. 

(A) Feeder or Service Load. It shall be permissible to 
compute the load of a feeder or service that supplies more 
than two dwelling units of a multifamily dwelling in accor- 
dance with Table 220.32 instead of Part II of this article 
where all the following conditions are met: 

(1) No dwelling unit is supplied by more than one feeder. 

(2) Each dwelling unit is equipped with electric cooking 
equipment. 

Exception: When the computed load for multifamily dwell- 
ings without electric cooking in Part II of this article ex- 
ceeds that computed under Part III for the identical load 
plus electric cooking (based on 8 kW per unit), the lesser of 
the two loads shall be permitted to be used. 

(3) Each dwelling unit is equipped with either electric 
space heating, air conditioning, or both. Feeders and 
service conductors whose demand load is determined 
by this optional calculation shall be permitted to have 
the neutral load determined by 220.22. 

(B) House Loads. House loads shall be computed in ac- 
cordance with Part II of this article and shall be in addition 
to the dwelling unit loads computed in accordance with 
Table 220.32. 

(C) Connected Loads. The computed load to which the 
demand factors of Table 220.32 apply shall include the 
following: 



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Table 220.32 Optional Calculations — Demand Factors for 
Three or More Multifamily Dwelling Units 

Number of Dwelling Units Demand Factor (Percent) 



3-5 

6-7 
8-10 

11 
12-13 
14-15 
16-17 
18-20 

21 
22-23 
24-25 
26-27 
28-30 

31 
32-33 
34-36 
37-38 
39-^2 
43-45 
46-50 
51-55 
56-61 
62 and over 



45 
44 
43 
42 
41 
40 
39 
38 
37 
36 
35 
34 
33 
32 
31 
30 
29 
28 
27 
26 
25 
24 
23 



(1) 1500 volt-amperes for each 2- wire, 20-ampere small- 
appliance branch circuit and each laundry branch cir- 
cuit specified in 220.16. 

(2) 33 volt-amperes/m 2 or 3 volt-amperes/ft 2 for general 
lighting and general-use receptacles. 

(3) The nameplate rating of all appliances that are fastened 
in place, permanently connected or located to be on a 
specific circuit, ranges, wall-mounted ovens, counter- 
mounted cooking units, clothes dryers, water heaters, 
and space heaters. If water heater elements are inter- 
locked so that all elements cannot be used at the same 
time, the maximum possible load shall be considered 
the nameplate load. 

(4) The nameplate ampere or kilovolt-ampere rating of all 
motors and of all low-power-factor loads. 

(5) The larger of the air-conditioning load or the space- 
heating load. 

220.33 Optional Calculation — Two Dwelling Units. 

Where two dwelling units are supplied by a single feeder 
and the computed load under Part II of this article exceeds 
that for three identical units computed under 220.32, the 
lesser of the two loads shall be permitted to be used. 

220.34 Optional Method — Schools. The calculation of a 
feeder or service load for schools shall be permitted in 
accordance with Table 220.34 in lieu of Part II of this 
article where equipped with electric space heating, air con- 



ditioning, or both. The connected load to which the demand 
factors of Table 220.34 apply shall include all of the inte- 
rior and exterior lighting, power, water heating, cooking, 
other loads, and the larger of the air-conditioning load or 
space-heating load within the building or structure. 

Feeders and service-entrance conductors whose demand 
load is determined by this optional calculation shall be per- 
mitted to have the neutral load determined by 220.22. 
Where the building or structure load is calculated by this 
optional method, feeders within the building or structure 
shall have ampacity as permitted in Part II of this article; 
however, the ampacity of an individual feeder shall not be 
required to be larger than the ampacity for the entire build- 
ing. 

This section shall not apply to portable classroom build- 
ings. 



Table 220.34 Optional Method — Demand Factors for 
Feeders and Service-Entrance Conductors for Schools 







Demand 






Factor 


Connected Load 




(Percent) 


First 33 VA/m 2 (3 VA/ft 2 ) at 




100 


Plus 






Over 33 to 220 VA/m 2 (3 to 20 VA/ft 2 ) 


at 


75 


Plus 






Remainder over 220 VA/m 2 (20 VA/ft 2 ) 


at 


25 



220.35 Optional Calculations for Determining Existing 
Loads. The calculation of a feeder or service load for ex- 
isting installations shall be permitted to use actual maxi- 
mum demand to determine the existing load under the fol- 
lowing conditions: 

(1) The maximum demand data is available for a 1-year 
period. 

Exception: If the maximum demand data for a 1 -year pe- 
riod is not available, the calculated load shall be permitted 
to be based on the maximum demand (measure of average 
power demand over a 15-minute period) continuously re- 
corded over a minimum 30-day period using a recording 
ammeter or power meter connected to the highest loaded 
phase of the feeder or service, based on the initial loading 
at the start of the recording. The recording shall reflect the 
maximum demand of the feeder or service by being taken 
when the building or space is occupied and shall include by 
measurement or calculation the larger of the heating or 
cooling equipment load, and other loads that may be peri- 
odic in nature due to seasonal or similar conditions. 

(2) The maximum demand at 125 percent plus the new 
load does not exceed the ampacity of the feeder or 
rating of the service. 



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Table 220.36 Optional Method — Permitted Load Calculations for Service and Feeder Conductors for New Restaurants 



Total Connected Load (kVA) 



All Electric Restaurant 
Calculated Loads (kVA) 



Not AH Electric Restaurant 
Calculated Loads (kVA) 



0-200 
201-325 
326-800 
Over 800 



80% 
10% (amount over 200) + 160.0 
50% (amount over 325) + 172.5 
50% (amount over 800) + 410.0 



100% 
50% (amount over 200) + 200.0 
45% (amount over 325) + 262.5 
20% (amount over 800) + 476.3 



Note: Add all electrical loads, including both heating and cooling loads, to compute the total connected load. Select the one demand factor that 
applies from the table, and multiply the total connected load by this single demand factor. 



(3) The feeder has overcurrent protection in accordance 
with 240.4, and the service has overload protection in 
accordance with 230.90. 



with Table 220.40 and shall be permitted to be combined 
as a single load in Table 220.41 for computing the total 
load. 



220.36 Optional Calculation — New Restaurants.. 

Calculation of a service or feeder load, where the feeder 
serves the total load, for a new restaurant shall be permitted 
in accordance with Table 220.36 in lieu of Part II of this 
article. 

The overload protection of the service conductors shall 
be in accordance with 230.90 and 240.4. 

Feeder conductors shall not be required to be of greater 
ampacity than the service conductors. 

Service or feeder conductors whose demand load is de- 
termined by this optional calculation shall be permitted to 
have the neutral load determined by 220.22. 

IV. Method for Computing Farm Loads 

220.40 Farm Loads — Buildings and Other Loads. 

(A) Dwelling Unit. The feeder or service load of a farm 
dwelling unit shall be computed in accordance with the 
provisions for dwellings in Part II or III of this article. 
Where the dwelling has electric heat and the farm has elec- 
tric grain-drying systems, Part III of this article shall not be 
used to compute the dwelling load where the dwelling and 
farm load are supplied by a common service. 

(B) Other Than Dwelling Unit. Where a feeder or service 
supplies a farm building or other load having two or more 
separate branch circuits, the load for feeders, service con- 
ductors, and service equipment shall be computed in accor- 
dance with demand factors not less than indicated in Table 
220.40. 

220.41 Farm Loads — Total. Where supplied by a com- 
mon service, the total load of the farm for service conduc- 
tors and service equipment shall be computed in accor- 
dance with the farm dwelling unit load and demand factors 
specified in Table 220.41. Where there is equipment in two 
or more farm equipment buildings or for loads having the 
same function, such loads shall be computed in accordance 



Table 220.40 Method for Computing Farm Loads for Other 
Than Dwelling Unit 



Ampere Load at 240 Volts Maximum 



Demand Factor 
(Percent) 



Loads expected to operate without 
diversity, but not less than 125 percent 
full-load current of the largest motor 
and not less than the first 60 amperes 
of load 

Next 60 amperes of all other loads 

Remainder of other load 



100 



50 

25 



Table 220.41 Method for Computing Total Farm Load 



Individual Loads Computed in 
Accordance with Table 220.40 



Demand Factor 
(Percent) 



Largest load 
Second largest load 
Third largest load 
Remaining loads 



100 
75 
65 
50 



Note: To this total load, add the load of the farm dwelling unit com- 
puted in accordance with Part II or III of this article. Where the 
dwelling has electric heat and the farm has electric grain-drying sys- 
tems, Part III of this article shall not be used to compute the dwelling 
load. 



ARTICLE 225 
Outside Branch Circuits and Feeders 



225.1 Scope. This article covers requirements for outside 
branch circuits and feeders run on or between buildings, 
structures, or poles on the premises; and electric equipment 
and wiring for the supply of utilization equipment that is 



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ARTICLE 225 — OUTSIDE BRANCH CIRCUITS AND FEEDERS 



located on or attached to the outside of buildings, struc- 
tures, or poles. 

FPN: For additional information on wiring over 600 volts, 
see ANSI C2-1997, National Electrical Safety Code. 

225.2 Other Articles. Application of other articles, includ- 
ing additional requirements to specific cases of equipment 
and conductors, is shown in Table 225.2. 

Table 225.2 Other Articles 



Equipment/Conductors 


Article 


Branch circuits 


210 


Class 1, Class 2, and Class 3 


725 


remote-control, signaling, and 




power-limited circuits 




Communications circuits 


800 


Community antenna television and radio 


820 


distribution systems 




Conductors for general wiring 


310 


Electrically driven or controlled irrigation 


675 


machines 




Electric signs and outline lighting 


600 


Feeders 


215 


Fire alarm systems 


760 


Fixed outdoor electric deicing and 


426 


snow-melting equipment 




Floating buildings 


553 


Grounding 


250 


Hazardous (classified) locations 


500 


Hazardous (classified) locations — specific 


510 


Marinas and boatyards 


555 


Messenger supported wiring 


396 


Open wiring on insulators 


398 


Over 600 volts, general 


490 


Overcurrent protection 


240 


Radio and television equipment 


810 


Services 


230 


Solar photovoltaic systems 


690 


Swimming pools, fountains, and similar 


680 


installations 




Use and identification of grounded 


200 


conductors 





I. General 

225.3 Calculation of Loads 600 Volts, Nominal, or Less. 

(A) Branch Circuits. The load on outdoor branch circuits 
shall be as determined by 220.3. 

(B) Feeders. The load on outdoor feeders shall be as de- 
termined by Part II of Article 220. 

225.4 Conductor Covering. Where within 3.0 m (10 ft) of 
any building or structure other than supporting poles or 
towers, open individual (aerial) overhead conductors shall 
be insulated or covered. Conductors in cables or raceways, 



except Type MI cable, shall be of the rubber-covered type 
or thermoplastic type and, in wet locations, shall comply 
with 310.8. Conductors for festoon lighting shall be of the 
rubber-covered or thermoplastic type. 

Exception: Equipment grounding conductors and 
grounded circuit conductors shall be permitted to be bare 
or covered as specifically permitted elsewhere in this Code. 

225.5 Size of Conductors 600 Volts, Nominal, or Less. 

The ampacity of outdoor branch-circuit and feeder conduc- 
tors shall be in accordance with 310.15 based on loads as 
determined under 220.3 and Part II of Article 220. 

225.6 Conductor Size and Support. 

(A) Overhead Spans. Open individual conductors shall 
not be smaller than the following: 

(1) For 600 volts, nominal, or less, 10 AWG copper or 8 
AWG aluminum for spans up to 15 m (50 ft) in length 
and 8 AWG copper or 6 AWG aluminum for a longer 
span, unless supported by a messenger wire 

(2) For over 600 volts, nominal, 6 AWG copper or 4 AWG 
aluminum where open individual conductors and 8 
AWG copper or 6 AWG aluminum where in cable 

(B) Festoon Lighting. Overhead conductors for festoon 
lighting shall not be smaller than 12 AWG unless the con- 
ductors are supported by messenger wires. In all spans ex- 
ceeding 12 m (40 ft), the conductors shall be supported by 
messenger wire. The messenger wire shall be supported by 
strain insulators. Conductors or messenger wires shall not 
be attached to any fire escape, downspout, or plumbing 
equipment. 

225.7 Lighting Equipment Installed Outdoors. 

(A) General. For the supply of lighting equipment in- 
stalled outdoors, the branch circuits shall comply with Ar- 
ticle 210 and 225.7(B) through (D). 

(B) Common Neutral. The ampacity of the neutral con- 
ductor shall not be less than the maximum net computed 
load current between the neutral and all ungrounded con- 
ductors connected to any one phase of the circuit. 

(C) 277 Volts to Ground. Circuits exceeding 120 volts, 
nominal, between conductors and not exceeding 277 volts, 
nominal, to ground shall be permitted to supply luminaires 
(lighting fixtures) for illumination of outdoor areas of in- 
dustrial establishments, office buildings, schools, stores, 
and other commercial or public buildings where the lumi- 
naires (fixtures) are not less than 900 mm (3 ft) from win- 
dows, platforms, fire escapes, and the like. 



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• 



(D) 600 Volts Between Conductors. Circuits exceeding 
277 volts, nominal, to ground and not exceeding 600 volts, 
nominal, between conductors shall be permitted to supply 
the auxiliary equipment of electric-discharge lamps in ac- 
cordance with 210.6(D)(1). 

225.9 Overcurrent Protection. Overcurrent protection 
shall be in accordance with 210.20 for branch circuits and 
Article 240 for feeders. 

225.10 Wiring on Buildings. The installation of outside 
wiring on surfaces of buildings shall be permitted for cir- 
cuits of not over 600 volts, nominal, as open wiring on 
insulators, as multiconductor cable, as Type MC cable, as 
Type MI cable, as messenger supported wiring, in rigid 
metal conduit, in intermediate metal conduit, in rigid non- 
metallic conduit, in cable trays, as cablebus, in wireways, 
in auxiliary gutters, in electrical metallic tubing, in flexible 
metal conduit, in liquidtight flexible metal conduit, in liq- 
uidtight flexible nonmetallic conduit, and in busways. Cir- 
cuits of over 600 volts, nominal, shall be installed as pro- 
vided in 300.37. Circuits for signs and outline lighting shall 
be installed in accordance with Article 600. 

225.11 Circuit Exits and Entrances. Where outside 
branch and feeder circuits leave or enter a building, the 
requirements of 230.52 and 230.54 shall apply. 

225.12 Open-Conductor Supports. Open conductors 
shall be supported on glass or porcelain knobs, racks, 
brackets, or strain insulators. 

225.14 Open-Conductor Spacings. 

(A) 600 Volts, Nominal, or Less. Conductors of 600 volts, 
nominal, or less, shall comply with the spacings provided 
in Table 230.51(C). 

(B) Over 600 Volts, Nominal. Conductors of over 600 
volts, nominal, shall comply with the spacings provided in 
110.36 and 490.24. 

(C) Separation from Other Circuits. Open conductors 
shall be separated from open conductors of other circuits or 
systems by not less than 100 mm (4 in.). 

(D) Conductors on Poles. Conductors on poles shall have 
a separation of not less than 300 mm (1 ft) where not 
placed on racks or brackets. Conductors supported on poles 
shall provide a horizontal climbing space not less than the 
following: 

(1) Power conductors below communications conductors 
— 750 mm (30 in.) 

(2) Power conductors alone or above communications con- 
ductors: 



a. 300 volts or less — 600 mm (24 in.) 

b. Over 300 volts — 750 mm (30 in.) 

(3) Communications conductors below power conductors 
— same as power conductors 

(4) Communications conductors alone — no requirement 

225.15 Supports over Buildings. Supports over a building 
shall be in accordance with 230.29. 

225.16 Point of Attachment to Buildings. The point of 
attachment to a building shall be in accordance with 
230.26. 

225.17 Means of Attachment to Buildings. The means of 
attachment to a building shall be in accordance with 
230.27. 

225.18 Clearance from Ground. Overhead spans of open 
conductors and open multiconductor cables of not over 600 
volts, nominal, shall conform to the following: 

(1) 3.0 m (10 ft) — above finished grade, sidewalks, or 
from any platform or projection from which they might 
be reached where the voltage does not exceed 150 volts 
to ground and accessible to pedestrians only 

(2) 3.7 m (12 ft) — over residential property and drive- 
ways, and those commercial areas not subject to truck 
traffic where the voltage does not exceed 300 volts to 
ground 

(3) 4.5 m (15 ft) — for those areas listed in the 3.7-m 
(12-ft) classification where the voltage exceeds 300 
volts to ground 

(4) 5.5 m (18 ft) — over public streets, alleys, roads, park- 
ing areas subject to truck traffic, driveways on other 
than residential property, and other land traversed by 
vehicles, such as cultivated, grazing, forest, and 
orchard 

225.19 Clearances from Buildings for Conductors of 
Not Over 600 Volts, Nominal. 

(A) Above Roofs. Overhead spans of open conductors and 
open multiconductor cables shall have a vertical clearance 
of not less than 2.5 m (8 ft) above the roof surface. The 
vertical clearance above the roof level shall be maintained 
for a distance not less than 900 mm (3 ft) in all directions 
from the edge of the roof. 

Exception No. 1: The area above a roof surface subject to 
pedestrian or vehicular traffic shall have a vertical clear- 
ance from the roof surface in accordance with the clear- 
ance requirements of 225.18. 

Exception No. 2: Where the voltage between conductors 
does not exceed 300, and the roof has a slope of 100 mm 



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ARTICLE 225 — OUTSIDE BRANCH CIRCUITS AND FEEDERS 



(4 in.) in 300 mm (12 in.) or greater, a reduction in clear- 
ance to 900 mm (3 ft) shall be permitted. 

Exception No. 3: Where the voltage between conductors 
does not exceed 300, a reduction in clearance above only 
the overhanging portion of the roof to not less than 450 mm 
(18 in.) shall be permitted if (1) not more than 1.8 m (6 ft) 
of the conductors, 1.2 m (4 ft) horizontally, pass above the 
roof overhang and (2) they are terminated at a through-the- 
roof raceway or approved support. 

Exception No. 4: The requirement for maintaining the ver- 
tical clearance 900 mm (3 ft) from the edge of the roof shall 
not apply to the final conductor span where the conductors 
are attached to the side of a building. 

(B) From Nonbuilding or Nonbridge Structures. From 
signs, chimneys, radio and television antennas, tanks, and 
other nonbuilding or nonbridge structures, clearances — 
vertical, diagonal, and horizontal — shall not be less than 
900 mm (3 ft). 

(C) Horizontal Clearances. Clearances shall not be less 
than 900 mm (3 ft). 

(D) Final Spans. Final spans of feeders or branch circuits 
shall comply with 225.19(D)(1), (2), and (3). 

(1) Clearance from Windows. Final spans to the building 
they supply, or from which they are fed, shall be permitted 
to be attached to the building, but they shall be kept not less 
than 900 mm (3 ft) from windows that are designed to be 
opened, and from doors, porches, balconies, ladders, stairs, 
fire escapes, or similar locations. 

Exception: Conductors run above the top level of a win- 
dow shall be permitted to be less than the 900-mm (3-ft) 
requirement. 

(2) Vertical Clearance. The vertical clearance of final 
spans above, or within 900 mm (3 ft) measured horizontally 
of, platforms, projections, or surfaces from which they 
might be reached shall be maintained in accordance with 
225.18. 

(3) Building Openings. The overhead branch-circuit and 
feeder conductors shall not be installed beneath openings 
through which materials may be moved, such as openings 
in farm and commercial buildings, and shall not be installed 
where they obstruct entrance to these buildings' openings. 

(E) Zone for Fire Ladders. Where buildings exceed three 
stories or 15 m (50 ft) in height, overhead lines shall be 
arranged, where practicable, so that a clear space (or zone) 
at least 1.8 m (6 ft) wide will be left either adjacent to the 
buildings or beginning not over 2.5 m (8 ft) from them to 
facilitate the raising of ladders when necessary for fire 
fighting. 



225.20 Mechanical Protection of Conductors. Mechan- 
ical .protection of conductors on buildings, structures, or 
poles shall be as provided for services in 230.50. 

225.21 Multiconductor Cables on Exterior Surfaces of 
Buildings. Supports for multiconductor cables on exterior 
surfaces of buildings shall be as provided in 230.51. 

225.22 Raceways on Exterior Surfaces of Buildings or 
Other Structures. Raceways on exterior surfaces of build- 
ings or other structures shall be raintight and arranged to 
drain. 



Exception: Flexible metal conduit, where permi 
348.12(1), shall not be required to be raintight. 



itted 



in 



225.24 Outdoor Lampholders. Where outdoor landhold- 
ers are attached as pendants, the connections to the circuit 
wires shall be staggered. Where such lampholders have 
terminals of a type that puncture the insulation and make 
contact with the conductors, they shall be attached only to 
conductors of the stranded type. 

225.25 Location of Outdoor Lamps. Locations of lamps 
for outdoor lighting shall be below all energized conduc- 
tors, transformers, or other electric utilization equipment, 
unless 

(1) Clearances or other safeguards are provided for 
relamping operations, or 

(2) Equipment is controlled by a disconnecting means that 
can be locked in the open position. 

225.26 Vegetation as Support. Vegetation such as trees 
shall not be used for support of overhead conductor spans. 

II. More Than One Building or Other Structure 

225.30 Number of Supplies. Where more than one build- 
ing or other structure is on the same property and under 
single management, each additional building or other struc- 
ture served that is on the load side of the service discon- 
necting means shall be supplied by one feeder or branch 
circuit unless permitted in 225.30(A) through (E). For the 
purpose of this section, a multiwire branch circuit shall be 
considered a single circuit. 

(A) Special Conditions. Additional feeders or branch cir- 
cuits shall be permitted to supply the following: 

(1) Fire pumps 

(2) Emergency systems 

(3) Legally required standby systems 

(4) Optional standby systems 

(5) Parallel power production systems 



• 



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ARTICLE 225 — OUTSIDE BRANCH CIRCUITS AND FEEDERS 



70-73 



(B) Special Occupancies. By special permission, addi- 
tional feeders or branch circuits shall be permitted for the 
following: 

(1) Multiple-occupancy buildings where there is no space 
available for supply equipment accessible to all occu- 
pants, or 

(2) A single building or other structure sufficiently large to 
make two or more supplies necessary. 

(C) Capacity Requirements. Additional feeders or branch 
circuits shall be permitted where the capacity requirements 
are in excess of 2000 amperes at a supply voltage of 600 
volts or less. 

(D) Different Characteristics. Additional feeders or 
branch circuits shall be permitted for different voltages, 
frequencies, or phases or for different uses, such as control 
of outside lighting from multiple locations. 

(E) Documented Switching Procedures. Additional feed- 
ers or branch circuits shall be permitted to supply installa- 
tions under single management where documented safe 
switching procedures are established and maintained for 
disconnection. 



225.33 Maximum Number of Disconnects. 

(A) General. The disconnecting means for each supply 
permitted by 225.30 shall consist of not more than six 
switches or six circuit breakers mounted in a single enclo- 
sure, in a group of separate enclosures, or in or on a switch- 
board. There shall be no more than six disconnects per 
supply grouped in any one location. 

Exception: For the purposes of this section, disconnecting 
means used solely for the control circuit of the ground-fault 
protection system, or the control circuit of the power- 
operated supply disconnecting means, installed as part of 
the listed equipment, shall not be considered a supply dis- 
connecting means. 

(B) Single-Pole Units. Two or three single-pole switches 
or breakers capable of individual operation shall be permit- 
ted on multiwire circuits, one pole for each ungrounded 
conductor, as one multipole disconnect, provided they are 
equipped with handle ties or a master handle to disconnect 
all ungrounded conductors with no more than six opera- 
tions of the hand. 



• 



225.31 Disconnecting Means. Means shall be provided 
for disconnecting all ungrounded conductors that supply or 
pass through the building or structure. 

225.32 Location. The disconnecting means shall be in- 
stalled either inside or outside of the building or structure 
served or where the conductors pass through the building or 
structure. The disconnecting means shall be at a readily 
accessible location nearest the point of entrance of the con- 
ductors. For the purposes of this section, the requirements 
in 230.6 shall be permitted to be utilized. 

Exception No. 1: For installations under single manage- 
ment, where documented safe switching procedures are es- 
tablished and maintained for disconnection, and where the 
installation is monitored by qualified individuals, the dis- 
connecting means shall be permitted to be located else- 
where on the premises. 

Exception No. 2: For buildings or other structures qualify- 
ing under the provisions of Article 685, the disconnecting 
means shall be permitted to be located elsewhere on the 
premises. 

Exception No. 3: For towers or poles used as lighting stan- 
dards, the disconnecting means shall be permitted to be 
located elsewhere on the premises. 

Exception No. 4: For poles or similar structures used only 
for support of signs installed in accordance with Article 
600, the disconnecting means shall be permitted to be lo- 
cated elsewhere on the premises. 



225.34 Grouping of Disconnects. 

(A) General. The two to six disconnects as permitted in 
225.33 shall be grouped. Each disconnect shall be marked 
to indicate the load served. 

Exception: One of the two to six disconnecting means per- 
mitted in 225.33, where used only for a water pump also 
intended to provide fire protection, shall be permitted to be 
located remote from the other disconnecting means. 

(B) Additional Disconnecting Means. The one or more 
additional disconnecting means for fire pumps or for emer- 
gency, legally required standby or optional standby system 
permitted by 225.30 shall be installed sufficiently remote 
from the one to six disconnecting means for normal supply 
to minimize the possibility of simultaneous interruption of 
supply. 

225.35 Access to Occupants. In a multiple-occupancy 
building, each occupant shall have access to the occupant's 
supply disconnecting means. 

Exception: In a multiple-occupancy building where elec- 
tric supply and electrical maintenance are provided by the 
building management and where these are under continu- 
ous building management supervision, the supply discon- 
necting means supplying more than one occupancy shall be 



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ARTICLE 225 —OUTSIDE BRANCH CIRCUITS AND FEEDERS 



permitted to be accessible to authorized management per- 
sonnel only. 

225.36 Suitable for Service Equipment. The disconnect- 
ing means specified in 225.31 shall be suitable for use as 
service equipment. 

Exception: For garages and outbuildings on residential 
property, a snap switch or a set of 3-way or 4-way snap 
switches shall be permitted as the disconnecting means. 

225.37 Identification. Where a building or structure has 
any combination of feeders, branch circuits, or services 
passing through it or supplying it, a permanent plaque or 
directory shall be installed at each feeder and branch-circuit 
disconnect location denoting all other services, feeders, or 
branch circuits supplying that building or structure or pass- 
ing through that building or structure and the area served by 
each. 

Exception No. 1: A plaque or directory shall not be re- 
quired for large-capacity multibuilding industrial installa- 
tions under single management, where it is ensured that 
disconnection can be accomplished by establishing and 
maintaining safe switching procedures. 

Exception No. 2: This identification shall not be required 
for branch circuits installed from a dwelling unit to a sec- 
ond building or structure. 

225.38 Disconnect Construction. Disconnecting means 
shall meet the requirements of 225.38(A) through (D). 

Exception: For garages and outbuildings on residential 
property, snap switches or sets of 3-way or 4-way snap 
switches shall be permitted as the disconnecting means. 

(A) Manually or Power Operable. The disconnecting 
means shall consist of either (1) a manually operable switch 
or a circuit breaker equipped with a handle or other suitable 
operating means or (2) a power-operable switch or circuit 
breaker, provided the switch or circuit breaker can be 
opened by hand in the event of a power failure. 

(B) Simultaneous Opening of Poles. Each building or 
structure disconnecting means shall simultaneously discon- 
nect all ungrounded supply conductors that it controls from 
the building or structure wiring system. 

(C) Disconnection of Grounded Conductor. Where the 
building or structure disconnecting means does not discon- 
nect the grounded conductor from the grounded conductors 
in the building or structure wiring, other means shall be 
provided for this purpose at the location of disconnecting 
means. A terminal or bus to which all grounded conductors 
can be attached by means of pressure connectors shall be 
permitted for this purpose. 



In a multisection switchboard, disconnects for the 
grounded conductor shall be permitted to be in any of the 
switchboard, provided any such switchboard is marked. 

(D) Indicating. The building or structure disconnecting 
means shall plainly indicate whether it is in the open or 
closed position. 

225.39 Rating of Disconnect. The feeder or branch-circuit 
disconnecting means shall have a rating of not less than the 
load to be carried, determined in accordance with Article 
220. In no case shall the rating be lower than specified in 
225.39(A), (B), (C), or (D). 

(A) One-Circuit Installation. For installations to supply 
only limited loads of a single branch circuit, the branch 
circuit disconnecting means shall have a rating of not less 
than 15 amperes. 

(B) Two-Circuit Installations. For installations consisting 
of not more than two 2-wire branch circuits, the feeder or 
branch-circuit disconnecting means shall have a rating of 
not less than 30 amperes. 

(C) One-Family Dwelling. For a one-family dwelling, the 
feeder disconnecting means shall have a rating of not less 
than 100 amperes, 3-wire. 

(D) All Others. For all other installations, the feeder or 
branch-circuit disconnecting means shall have a rating of 
not less than 60 amperes. 

225.40 Access to Overcurrent Protective Devices. Where 
a feeder overcurrent device is not readily accessible, 
branch-circuit overcurrent devices shall be installed on the 
load side, shall be mounted in a readily accessible location, 
and shall be of a lower ampere rating than the feeder over- 
current device. 

III. Over 600 Volts 

225.50 Sizing of Conductors. The sizing of conductors 
over 600 volts shall be in accordance with 210.19(B) for 
branch circuits and 215.2(B) for feeders. 

225.51 Isolating Switches. Where oil switches or air, oil, 
vacuum, or sulfur hexafluoride circuit breakers constitute a 
building disconnecting means, an isolating switch with vis- 
ible break contacts and meeting the requirements of 
230.204(B), (C), and (D) shall be installed on the supply 
side of the disconnecting means and all associated equip- 
ment. 

Exception: The isolating switch shall not be required 
where the disconnecting means is mounted on removable 
truck panels or metal-enclosed switchgear units that cannot 



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ARTICLE 230 — SERVICES 



70-75 



be opened unless the circuit is disconnected and that, when 
removed from the normal operating position, automatically 
disconnect the circuit breaker or switch from all energized 
parts. 

225.52 Location. A building or structure disconnecting 
means shall be located in accordance with 225.31, or it 
shall be electrically operated by a similarly located remote- 
control device. 

225.53 Type. Each building or structure disconnect shall 
simultaneously disconnect all ungrounded supply conduc- 
tors it controls and shall have a fault-closing rating not less 
than the maximum available short-circuit current available 
at its supply terminals. 

Where fused switches or separately mounted fuses are 
installed, the fuse characteristics shall be permitted to con- 
tribute to the fault closing rating of the disconnecting 
means. 

225.60 Clearances over Roadways, Walkways, Rail, 
Water, and Open Land. 

(A) 22 kV Nominal to Ground or Less. The clearances 
over roadways, walkways, rail, water, and open land for 
conductors and live parts up to 22 kV nominal to ground or 
less shall be not less than the values shown in Table 225.60. 

(B) Over 22 kV Nominal to Ground. Clearances for the 
categories shown in Table 225.60 shall be increased by 
10 mm (0.4 in.) per kV above 22,000 volts. 

(C) Special Cases. For special cases, such as where cross- 
ings will be made over lakes, rivers, or areas using large 
vehicles such as mining operations, specific designs shall 
be engineered considering the special circumstances and 
shall be approved by the authority having jurisdiction. 

FPN: For additional information, see ANSI C2-1997, Na- 
tional Electrical Safety Code. 



Table 225.60 Clearances over Roadways, Walkways, Rail, 
Water, and Open Land 



Clearance 


Location 


m 


ft 


Open land subject to vehicles, 


5.6 


18.5 


cultivation, or grazing 






Roadways, driveways, parking lots, and 


5.6 


18.5 


alleys 






Walkways 


4.1 


13.5 


Rails 


8.1 


26.5 


Spaces and ways for pedestrians and 


4.4 


14.5 


restricted traffic 






Water areas not suitable for boating 


5.2 


17 



225.61 Clearances over Buildings and Other 
Structures. 

(A) 22 kV Nominal to Ground or Less. The clearances 
over buildings and other structures for conductors and live 
parts up to 22 kV, nominal, to ground or less shall be not 
less than the values shown in Table 225.61. 

(B) Over 22 kV Nominal to Ground. Clearances for the 
categories shown in Table 225.61 shall be increased by 
10 mm (0.4 in.) per kV above 22,000 volts. 

FPN: For additional information see ANSI C2-1997, Na- 
tional Electrical Safety Code. 



Table 225.61 Clearances over Buildings and Other 
Structures 



Clearance from 
Conductors or 
Live Parts from: 



Horizontal 



Vertical 



m 



m ft 



Building walls, 2.3 7.5 

projections, and 

windows 
Balconies, catwalks, 2.3 7.5 

and similar areas 

accessible to 

people 
Over or under roofs — — 

or projections not 

readily accessible 

to people 
Over roofs — — 

accessible to 

vehicles but not 

trucks 
Over roofs — — 

accessible to 

trucks 
Other structures 2.3 7.5 



4.1 



3.8 



4.1 



5.6 



13.5 



12.5 



13.5 



18.5 



ARTICLE 230 

Services 

230.1 Scope. This article covers service conductors and 
equipment for control and protection of services and their 
installation requirements. 

FPN: See Figure 230.1. 

I. General 

230.2 Number of Services. A building or other structure 
served shall be supplied by only one service unless permit- 
ted in 230.2(A) through (D). For the purpose of 230.40, 
Exception No. 2 only, underground sets of conductors, 



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ARTICLE 230 — SERVICES 



General Part I 

Overhead Service-Drop Conductors Part II 

Underground Service-Lateral Conductors Part III 

Service-Entrance Conductors Part IV 

Service Equipment — General PartV 

Service Equipment— Disconnecting Means Part VI 

Service Equipment — Overcurrent Protection Part VII 

Services Exceeding 600 Volts, Nominal Part VIII 

Source 



Overhead 
Last pole 


> 


k 


Underground 
Street main 


Part II Service drop 
230.24 Clearances 

Service head 




Service lateral Part III 

Depth of burial 230.49 
and protection 

Terminal box, 
meter, or other 










enclosure 










Service-entrance 
conductors 


Part IV 


Service equipment — general 
Grounding 


<! 


!> , 


PartV 
Article 250 



Disconnecting means 
Overcurrent protection 



Part VI 
Part VII 



Branch circuits 
Feeders 



Articles 210, 225 
Articles 215, 225 



Figure 230.1 Services. 

1/0 AWG and larger, running to the same location and con- 
nected together at their supply end but not connected to- 
gether at their load end shall be considered to be supplying 
one service. 

(A) Special Conditions. Additional services shall be per- 
mitted to supply the following: 

(1) Fire pumps 

(2) Emergency systems 

(3) Legally required standby systems 

(4) Optional standby systems 

(5) Parallel power production systems 

(B) Special Occupancies. By special permission, addi- 
tional services shall be permitted for the following: 

(1) Multiple-occupancy buildings where there is no avail- 
able space for service equipment accessible to all oc- 
cupants, or 

(2) A single building or other structure sufficiently large to 
make two or more services necessary 



(C) Capacity Requirements. Additional services shall be 
permitted under any of the following: 

(1) Where the capacity requirements are in excess of 2000 
amperes at a supply voltage of 600 volts or less 

(2) Where the load requirements of a single-phase installa- 
tion are greater than the serving agency normally sup- 
plies through one service 

(3) By special permission 

(D) Different Characteristics. Additional services shall 
be permitted for different voltages, frequencies, or phases, 
or for different uses, such as for different rate schedules. 

(E) Identification. Where a building or structure is sup- 
plied by more than one service, or any combination of 
branch circuits, feeders, and services, a permanent plaque 
or directory shall be installed at each service disconnect 
location denoting all other services, feeders, and branch 
circuits supplying that building or structure and the area 
served by each. See 225.37. 

230.3 One Building or Other Structure Not to Be Sup- 
plied Through Another. Service conductors supplying a 
building or other structure shall not pass through the inte- 
rior of another building or other structure. 

230.6 Conductors Considered Outside the Building. 

Conductors shall be considered outside of a building or 
other structure under any of the following conditions: 

(1) Where installed under not less than 50 mm (2 in.) of 
concrete beneath a building or other structure 

(2) Where installed within a building or other structure in a 
raceway that is encased in concrete or brick not less 
than 50 mm (2 in.) thick 

(3) Where installed in any vault that meets the construction 
requirements of Article 450, Part III 

(4) Where installed in conduit and under not less than 
450 mm (18 in.) of earth beneath a building or other 
structure 

230.7 Other Conductors in Raceway or Cable. Con- 
ductors other than service conductors shall not be installed 
in the same service raceway or service cable. 

Exception No. 1: Grounding conductors and bonding 
jumpers. 

Exception No. 2: Load management control conductors 
having overcurrent protection. 

230.8 Raceway Seal. Where a service raceway enters a 
building or structure from an underground distribution sys- 
tem, it shall be sealed in accordance with 300.5(G). Spare 
or unused raceways shall also be sealed. Sealants shall be 



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ARTICLE 230 — SERVICES 



70-77 



identified for use with the cable insulation, shield, or other 
components. 

230.9 Clearance from Building Openings. Service con- 
ductors and final spans shall comply with 230.9(A), (B), 
and (C). 

(A) Clearance from Windows. Service conductors in- 
stalled as open conductors or multiconductor cable without 
an overall outer jacket shall have a clearance of not less 
than 900 mm (3 ft) from windows that are designed to be 
opened, doors, porches, balconies, ladders, stairs, fire es- 
capes, or similar locations. 

Exception: Conductors run above the top level of a win- 
dow shall be permitted to be less than the 900-mm (3 -ft) 
requirement. 

(B) Vertical Clearance. The vertical clearance of final 
spans above, or within 900 mm (3 ft) measured horizontally 
of, platforms, projections, or surfaces from which they 
might be reached shall be maintained in accordance with 
230.24(B). 

(C) Building Openings. Overhead service conductors 
shall not be installed beneath openings through which ma- 
terials may be moved, such as openings in farm and com- 
mercial buildings, and shall not be installed where they 
obstruct entrance to these building openings. 

230.10 Vegetation as Support. Vegetation such as trees 
shall not be used for support of overhead service conduc- 
tors. 

II. Overhead Service-Drop Conductors 

230.22 Insulation or Covering. Individual conductors 
shall be insulated or covered. 

Exception: The grounded conductor of a multiconductor 
cable shall be permitted to be bare. 

230.23 Size and Rating. 

(A) General. Conductors shall have sufficient ampacity to 
carry the current for the load as computed in accordance 
with Article 220 and shall have adequate mechanical 
strength. 

(B) Minimum Size. The conductors shall not be smaller 
than 8 AWG copper or 6 AWG aluminum or copper-clad 
aluminum. 

Exception: Conductors supplying only limited loads of a 
single branch circuit — such as small polyphase power, 
controlled water heaters, and similar loads — shall not be 
smaller than 12 AWG hard-drawn copper or equivalent. 



(C) Grounded Conductors. The grounded conductor shall 
not be less than the minimum size as required by 
250.24(B). 

230.24 Clearances. Service-drop conductors shall not be 
readily accessible and shall comply with 230.24(A) through 

(D) for services not over 600 volts, nominal. 

(A) Above Roofs. Conductors shall have a vertical clear- 
ance of not less than 2.5 m (8 ft) above the roof surface. 
The vertical clearance above the roof level shall be main- 
tained for a distance of not less than 900 mm (3 ft) in all 
directions from the edge of the roof. 

Exception No. 1: The area above a roof surface subject to 
pedestrian or vehicular traffic shall have a vertical clear- 
ance from the roof surface in accordance with the clear- 
ance requirements of 230.24(B). 

Exception No. 2: Where the voltage between conductors 
does not exceed 300 and the roof has a slope of 100 mm 
(4 in.) in 300 mm (12 in.), or greater, a reduction in clear- 
ance to 900 mm (3 ft) shall be permitted. 

Exception No. 3: Where the voltage between conductors 
does not exceed 300, a reduction in clearance above only 
the overhanging portion of the roof to not less than 450 mm 
(18 in.) shall be permitted if (1) not more than 1.8 m (6 ft) 
of service-drop conductors, 1.2 m (4 ft) horizontally, pass 
above the roof overhang, and (2) they are terminated at a 
through-the-roof raceway or approved support. 

FPN: See 230.28 for mast supports. 

Exception No. 4: The requirement for maintaining the ver- 
tical clearance 900 mm (3 ft) from the edge of the roof shall 
not apply to the final conductor span where the service 
drop is attached to the side of a building. 

(B) Vertical Clearance from Ground. Service-drop con- 
ductors, where not in excess of 600 volts, nominal, shall 
have the following minimum clearance from final grade: 

(1) 3.0 m (10 ft) — at the electric service entrance to 
buildings, also at the lowest point of the drip loop of 
the building electric entrance, and above areas or side- 
walks accessible only to pedestrians, measured from 
final grade or other accessible surface only for service- 
drop cables supported on and cabled together with a 
grounded bare messenger where the voltage does not 
exceed 150 volts to ground 

(2) 3.7 m (12 ft) — over residential property and drive- 
ways, and those commercial areas not subject to truck 
traffic where the voltage does not exceed 300 volts to 
ground 

(3) 4.5 m (15 ft) — for those areas listed in the 3.7 m 
(12 ft) classification where the voltage exceeds 300 
volts to ground 



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ARTICLE 230 — SERVICES 



(4) 5.5 m (18 ft) — over public streets, alleys, roads, park- 
ing areas subject to truck traffic, driveways on other 
than residential property, and other land such as culti- 
vated, grazing, forest, and orchard 

(C) Clearance from Building Openings. See 230.9. 

(D) Clearance from Swimming Pools. See 680.8. 

230.26 Point of Attachment. The point of attachment of 
the service-drop conductors to a building or other structure 
shall provide the minimum clearances as specified in 
230.24. In no case shall this point of attachment be less 
than 3.0 m (10 ft) above finished grade. 

230.27 Means of Attachment. Multiconductor cables used 
for service drops shall be attached to buildings or other 
structures by fittings identified for use with service conduc- 
tors. Open conductors shall be attached to fittings identified 
for use with service conductors or to noncombustible, non- 
absorbent insulators securely attached to the building or 
other structure. 

230.28 Service Masts as Supports. Where a service mast 
is used for the support of service-drop conductors, it shall 
be of adequate strength or be supported by braces or guys 
to withstand safely the strain imposed by the service drop. 
Where raceway-type service masts are used, all raceway 
fittings shall be identified for use with service masts. Only 
power service-drop conductors shall be permitted to be at- 
tached to a service mast. 

230.29 Supports over Buildings. Service-drop conductors 
passing over a roof shall be securely supported by substan- 
tial structures. Where practicable, such supports shall be 
independent of the building. 

III. Underground Service-Lateral Conductors 

230.30 Insulation. Service-lateral conductors shall be in- 
sulated for the applied voltage. 

Exception: A grounded conductor shall be permitted to be 
uninsulated as follows: 

(a) Bare copper used in a raceway. 

(b) Bare copper for direct burial where bare copper is 
judged to be suitable for the soil conditions. 

(c) Bare copper for direct burial without regard to soil 
conditions where part of a cable assembly identified for 
underground use. 

(d) Aluminum or copper-clad aluminum without individual 
insulation or covering where part of a cable assembly 
identified for underground use in a raceway or for di- 
rect burial. 



230.31 Size and Rating. 

(A) General. Service-lateral conductors shall have suffi- 
cient ampacity to carry the current for the load as computed 
in accordance with Article 220 and shall have adequate 
mechanical strength. 

(B) Minimum Size. The conductors shall not be smaller 
than 8 AWG copper or 6 AWG aluminum or copper-clad 
aluminum. 

Exception: Conductors supplying only limited loads of a 
single branch circuit — such as small polyphase power, 
controlled water heaters, and similar loads — shall not be 
smaller than 12 AWG copper or 10 AWG aluminum or 
copper-clad aluminum. 

(C) Grounded Conductors. The grounded conductor shall 
not be less than the minimum size required by 250.24(B). 

230.32 Protection Against Damage. Underground ser- 
vice-lateral conductors shall be protected against damage in 
accordance with 300.5. Service-lateral conductors entering 
a building shall be installed in accordance with 230.6 or 
protected by a raceway wiring method identified in 230.43. 

230.33 Spliced Conductors. Service-lateral conductors 
shall be permitted to be spliced or tapped in accordance 
with 110.14, 300.5(E), 300.13, and 300.15. 

IV. Service-Entrance Conductors 

230.40 Number of Service-Entrance Conductor Sets. 

Each service drop or lateral shall supply only one set of 
service-entrance conductors. 

Exception No. 1: A building with one or more than one 
occupancy shall be permitted to have one set of service- 
entrance conductors for each service of different character- 
istics, as defined in 230.2(D), run to each occupancy or 
group of occupancies. 

Exception No. 2: Where two to six service disconnecting 
means in separate enclosures are grouped at one location 
and supply separate loads from one service drop or lateral, 
one set of service-entrance conductors shall be permitted to 
supply each or several such service equipment enclosures. 

Exception No. 3: A single-family dwelling unit and a sepa- 
rate structure shall be permitted to have one set of service- 
entrance conductors run to each from a single service drop 
or lateral. 

Exception No. 4: A two-family dwelling or a multifamily 
dwelling shall be permitted to have one set of service- 
entrance conductors installed to supply the circuits covered 
in 210.25. 



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ARTICLE 230 — SERVICES 



70-79 



Exception No. 5: One set of service-entrance conductors 
connected to the supply side of the normal service discon- 
necting means shall be permitted to supply each or several- 
systems covered by 230.82(4) or (5). 

230.41 Insulation of Service-Entrance Conductors. 

Service-entrance conductors entering or on the exterior of 
buildings or other structures shall be insulated. 

Exception: A grounded conductor shall be permitted to be 
uninsulated as follows: 

(a) Bare copper used in a raceway or part of a service 
cable assembly. 

(b) Bare copper for direct burial where bare copper is 
judged to be suitable for the soil conditions. 

(c) Bare copper for direct burial without regard to soil 
conditions where part of a cable assembly identified for 
underground use. 

(d) Aluminum or copper-clad aluminum without individual 
insulation or covering where part of a cable assembly 
or identified for underground use in a raceway, or for 
direct burial. 

(e) Bare conductors used in an auxiliary gutter. 

230.42 Minimum Size and Rating. 

(A) General. The ampacity of the service-entrance con- 
ductors before the application of any adjustment or correc- 
tion factors shall not be less than either (1) or (2). Loads 
shall be determined in accordance with Article 220. Am- 
pacity shall be determined from 310.15. The maximum al- 
lowable current of busways shall be that value for which 
the busway has been listed or labeled. 

(1) The sum of the noncontinuous loads plus 125 percent 
of continuous loads 

(2) The sum of the noncontinuous load plus the continuous 
load if the service-entrance conductors terminate in an 
overcurrent device where both the overcurrent device 
and its assembly are listed for operation at 100 percent 
of their rating 

(B) Specific Installations. In addition to the requirements 
of 230.42(A), the minimum ampacity for ungrounded con- 
ductors for specific installations shall not be less than the 
rating of the service disconnecting means specified in 
230.79(A) through (D). 

(C) Grounded Conductors. The grounded conductor shall 
not be less than the minimum size as required by 
250.24(B). 

230.43 Wiring Methods for 600 Volts, Nominal, or Less. 

Service-entrance conductors shall be installed in accor- 
dance with the applicable requirements of this Code cover- 



ing the type of wiring method used and shall be limited to 
the following methods: 

(1) Open wiring on insulators 

(2) Type IGS cable 

(3) Rigid metal conduit 

(4) Intermediate metal conduit 

(5) Electrical metallic tubing 

(6) Electrical nonmetallic tubing (ENT) 

(7) Service-entrance cables 

(8) Wireways 

(9) Busways 

(10) Auxiliary gutters 

(11) Rigid nonmetallic conduit 

(12) Cablebus 

(13) Type MC cable 

(14) Mineral-insulated, metal-sheathed cable 

(15) Flexible metal conduit not over 1.8 m (6 ft) long or 
liquidtight flexible metal conduit not over 1.8 m (6 ft) 
long between raceways, or between raceway and ser- 
vice equipment, with equipment bonding jumper 
routed with the flexible metal conduit or the liq- 
uidtight flexible metal conduit according to the provi- 
sions of 250.102(A), (B), (C), and (E) 

(16) Liquidtight flexible nonmetallic conduit 

230.44 Cable Trays. Cable tray systems shall be permitted 
to support cable used as service-entrance conductors. 

230.46 Spliced Conductors. Service-entrance conductors 
shall be permitted to be spliced or tapped in accordance 
with 110.14, 300.5(E), 300.13, and 300.15. 

230.49 Protection Against Physical Damage — 
Underground. Underground service-entrance conductors 
shall be protected against physical damage in accordance 
with 300.5. 

230.50 Protection of Open Conductors and Cables 
Against Damage — Above Ground. Service-entrance 
conductors installed above ground shall be protected 
against physical damage as specified in 230.50(A) or (B). 

(A) Service Cables. Service cables, where subject to 
physical damage, shall be protected by any of the follow- 
ing: 

(1) Rigid metal conduit 

(2) Intermediate metal conduit 

(3) Schedule 80 rigid nonmetallic conduit 

(4) Electrical metallic tubing 

(5) Other approved means 

(B) Other Than Service Cable. Individual open con- 
ductors and cables other than service cables shall not be 



NATIONAL ELECTRICAL CODE 



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70-80 



ARTICLE 230 — SERVICES 



installed within 3.0 m (10 ft) of grade level or where ex- 
posed to physical damage. 

Exception: Type MI and Type MC cable shall be permitted 
within 3.0 m (10 ft) of grade level where not exposed to 
physical damage or where protected in accordance with 
300.5(D). 

230.51 Mounting Supports. Cables or individual open 
service conductors shall be supported as specified in 
230.51(A), (B), or (C). 

(A) Service Cables. Service cables shall be supported by 
straps or other approved means within 300 mm (12 in.) of 
every service head, gooseneck, or connection to a raceway 
or enclosure and at intervals not exceeding 750 mm 
(30 in.). 

(B) Other Cables. Cables that are not approved for 
mounting in contact with a building or other structure shall 
be mounted on insulating supports installed at intervals not 
exceeding 4.5 m (15 ft) and in a manner that will maintain 
a clearance of not less than 50 mm (2 in.) from the surface 
over which they pass. 

(C) Individual Open Conductors. Individual open con- 
ductors shall be installed in accordance with Table 
230.51(C). Where exposed to the weather, the conductors 
shall be mounted on insulators or on insulating supports 
attached to racks, brackets, or other approved means. 
Where not exposed to the weather, the conductors shall be 
mounted on glass or porcelain knobs. 

230.52 Individual Conductors Entering Buildings or 
Other Structures. Where individual open conductors enter 
a building or other structure, they shall enter through roof 
bushings or through the wall in an upward slant through 
individual, noncombustible, nonabsorbent insulating tubes. 
Drip loops shall be formed on the conductors before they 
enter the tubes. 

230.53 Raceways to Drain. Where exposed to the 
weather, raceways enclosing service-entrance conductors 

Table 230.51(C) Supports 



shall be raintight and arranged to drain. Where embedded 
in masonry, raceways shall be arranged to drain. 

Exception: As permitted in 348.12(1). 

230.54 Overhead Service Locations. 

(A) Raintight Service Head. Service raceways shall be 
equipped with a raintight service head at the point of con- 
nection to service-drop conductors. 

(B) Service Cable Equipped with Raintight Service 
Head or Gooseneck. Service cables shall be equipped with 
a raintight service head. 

Exception: Type SE cable shall be permitted to be formed 
in a gooseneck and taped with a self-sealing weather- 
resistant thermoplastic. 

(C) Service Heads Above Service-Drop Attachment. 

Service heads and goosenecks in service-entrance cables 
shall be located above the point of attachment of the 
service-drop conductors to the building or other structure. 

Exception: Where it is impracticable to locate the service 
head above the point of attachment, the service head loca- 
tion shall be permitted not farther than 600 mm (24 in.) 
from the point of attachment. 

(D) Secured. Service cables shall be held securely in 
place. 

(E) Separately Bushed Openings. Service heads shall 
have conductors of different potential brought out through 
separately bushed openings. 

Exception: For jacketed multiconductor service cable 
without splice. 

(F) Drip Loops. Drip loops shall be formed on individual 
conductors. To prevent the entrance of moisture, service- 
entrance conductors shall be connected to the service-drop 
conductors either (1) below the level of the service head 
or (2) below the level of the termination of the service- 
entrance cable sheath. 





Maximum Distance Between 
Supports 




Minimum Clearance 




Between Conductors From Surface 


MaximumVolts 


m ft 


mm 


in. mm in. 


600 
600 
300 
600* 


2.7 9 
4.5 15 
1.4 4'/ 2 
1.4* 4 ] / 2 * 


150 
300 

75 

65* 


6 50 2 

12 50 2 

3 50 2 

2'/ 2 * 25* 1* 



*Where not exposed to weather. 



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ARTICLE 230 — SERVICES 



70-81 



(G) Arranged That Water Will Not Enter Service Race- 
way or Equipment. Service-drop conductors and service- 
entrance conductors shall be arranged so that water will not 
enter service raceway or equipment. 

230.56 Service Conductor with the Higher Voltage to 
Ground. On a 4-wire, delta-connected service where the 
midpoint of one phase winding is grounded, the service 
conductor having the higher phase voltage to ground shall 
be durably and permanently marked by an outer finish that: 
is orange in color, or by other effective means, at each 
termination or junction point. 

V. Service Equipment — General 

230.62 Service Equipment — Enclosed or Guarded. 

Energized parts of service equipment shall be enclosed as 
specified in 230.62(A) or guarded as specified in 
230.62(B). 

(A) Enclosed. Energized parts shall be enclosed so that 
they will not be exposed to accidental contact or shall be 
guarded as in 230.62(B). 

(B) Guarded. Energized parts that are not enclosed shall 
be installed on a switchboard, panelboard, or control board 
and guarded in accordance with 110.18 and 110.27. Where 
energized parts are guarded as provided in 110.27(A)(1) 
and (2), a means for locking or sealing doors providing 
access to energized parts shall be provided. 

230.66 Marking. Service equipment rated at 600 volts or 
less shall be marked to identify it as being suitable for use 
as service equipment. Individual meter socket enclosures 
shall not be considered service equipment. 

VI. Service Equipment — Disconnecting Means 

230.70 General. Means shall be provided to disconnect all 
conductors in a building or other structure from the service- 
entrance conductors. 

(A) Location. The service disconnecting means shall be 
installed in accordance with 230.70(A)(1), (2), and (3). 

(1) Readily Accessible Location. The service disconnect- 
ing means shall be installed at a readily accessible location 
either outside of a building or structure or inside nearest the 
point of entrance of the service conductors. 

(2) Bathrooms. Service disconnecting means shall not be 
installed in bathrooms. 

(3) Remote Control. Where a remote control device(s) is 
used to actuate the service disconnecting means, the service 



disconnecting means shall be located in accordance with 
230.70(A)(1). 

(B) Marking. Each service disconnect shall be perma- 
nently marked to identify it as a service disconnect. 

(C) Suitable for Use. Each service disconnecting means 
shall be suitable for the prevailing conditions. Service 
equipment installed in hazardous (classified) locations shall 
comply with the requirements of Articles 500 through 517. 

230.71 Maximum Number of Disconnects. 

(A) General. The service disconnecting means for each 
service permitted by 230.2, or for each set of service- 
entrance conductors permitted by 230.40, Exception Nos. 
1, 3, 4, or 5, shall consist of not more than six switches or 
sets of circuit breakers, or a combination of not more than 
six switches and sets of circuit breakers, mounted in a 
single enclosure, in a group of separate enclosures, or in or 
on a switchboard. There shall be no more than six sets of 
disconnects per service grouped in any one location. For 
the purpose of this section, disconnecting means used 
solely for power monitoring equipment, or the control cir- 
cuit of the ground-fault protection system or power- 
operable service disconnecting means, installed as part of 
the listed equipment, shall not be considered a service dis- 
connecting means. 

(B) Single-Pole Units. Two or three single-pole switches 
or breakers, capable of individual operation, shall be per- 
mitted on multiwire circuits, one pole for each ungrounded 
conductor, as one multipole disconnect, provided they are 
equipped with handle ties or a master handle to disconnect 
all conductors of the service with no more than six opera- 
tions of the hand. 

FPN: See 408.16(A) for service equipment in panelboards, 
and see 430.95 for service equipment in motor control 
centers. 

230.72 Grouping of Disconnects. 

(A) General. The two to six disconnects as permitted in 
230.71 shall be grouped. Each disconnect shall be marked 
to indicate the load served. 

Exception: One of the two to six service disconnecting 
means permitted in 230. 71, where used only for a water 
pump also intended to provide fire protection, shall be per- 
mitted to be located remote from the other disconnecting 
means. 

(B) Additional Service Disconnecting Means. The one or 

more additional service disconnecting means for fire 
pumps, for legally required standby, or for optional standby 
services permitted by 230.2 shall be installed remote from 
the one to six service disconnecting means for normal ser- 



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ARTICLE 230 — SERVICES 



vice to minimize the possibility of simultaneous interrup- 
tion of supply. 

(C) Access to Occupants. In a multiple-occupancy build- 
ing, each occupant shall have access to the occupant's ser- 
vice disconnecting means. 

Exception: In a multiple-occupancy building where elec- 
tric service and electrical maintenance are provided by the 
building management and where these are under continu- 
ous building management supervision, the service discon- 
necting means supplying more than one occupancy shall be 
permitted to be accessible to authorized management per- 
sonnel only. 

230.74 Simultaneous Opening of Poles. Each service dis- 
connect shall simultaneously disconnect all ungrounded 
service conductors that it controls from the premises wiring 
system. 

230.75 Disconnection of Grounded Conductor. Where 
the service disconnecting means does not disconnect the 
grounded conductor from the premises wiring, other means 
shall be provided for this purpose in the service equipment. 
A terminal or bus to which all grounded conductors can be 
attached by means of pressure connectors shall be permit- 
ted for this purpose. In a multisection switchboard, discon- 
nects for the grounded conductor shall be permitted to be in 
any section of the switchboard, provided any such switch- 
board section is marked. 

230.76 Manually or Power Operable. The service dis- 
connecting means for ungrounded service conductors shall 
consist of either (1) a manually operable switch or circuit 
breaker equipped with a handle or other suitable operating 
means or (2) a power-operated switch or circuit breaker, 
provided the switch or circuit breaker can be opened by 
hand in the event of a power supply failure. 

230.77 Indicating. The service disconnecting means shall 
plainly indicate whether it is in the open or closed position. 

230.79 Rating of Service Disconnecting Means. The ser- 
vice disconnecting means shall have a rating not less than 
the load to be carried, determined in accordance with Ar- 
ticle 220. In no case shall the rating be lower than specified 
in 230.79(A), (B), (C), or (D). 

(A) One-Circuit Installation. For installations to supply 
only limited loads of a single branch circuit, the service 
disconnecting means shall have a rating of not less than 15 
amperes. 

(B) Two-Circuit Installations. For installations consisting 
of not more than two 2-wire branch circuits, the service 



disconnecting means shall have a rating of not less than 30 
amperes. 

(C) One-Family Dwelling. For a one-family dwelling, the 
service disconnecting means shall have a rating of not less 
than 100 amperes, 3- wire. 

(D) All Others. For all other installations, the service dis- 
connecting means shall have a rating of not less than 60 
amperes. 

230.80 Combined Rating of Disconnects. Where the ser- 
vice disconnecting means consists of more than one switch 
or circuit breaker, as permitted by 230.71, the combined 
ratings of all the switches or circuit breakers used shall not 
be less than the rating required by 230.79. 

230.81 Connection to Terminals. The service conductors 
shall be connected to the service disconnecting means by 
pressure connectors, clamps, or other approved means. 
Connections that depend on solder shall not be used. 

230.82 Equipment Connected to the Supply Side of 
Service Disconnect. Only the following equipment shall be 
permitted to be connected to the supply side of the service 
disconnecting means: 

(1) Cable limiters or other current-limiting devices. 

(2) Meters, meter sockets, or meter disconnect switches 
nominally rated not in excess of 600 volts, provided all 
metal housings and service enclosures are grounded. 

(3) Instrument transformers (current and voltage), high- 
impedance shunts, load management devices, and surge 
arresters. 

(4) Taps used only to supply load management devices, 
circuits for standby power systems, fire pump equip- 
ment, and fire and sprinkler alarms, if provided with 
service equipment and installed in accordance with re- 
quirements for service-entrance conductors. 

(5) Solar photovoltaic systems, fuel cell systems, or inter- 
connected electric power production sources. 

(6) Control circuits for power-operable service disconnect- 
ing means, if suitable overcurrent protection and dis- 
connecting means are provided. 

(7) Ground-fault protection systems where installed as part 
of listed equipment, if suitable overcurrent protection 
and disconnecting means are provided. 

VII. Service Equipment — Overcurrent Protection 

230.90 Where Required. Each ungrounded service con- 
ductor shall have overload protection. 

(A) Ungrounded Conductor. Such protection shall be 
provided by an overcurrent device in series with each un- 



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ARTICLE 230 — SERVICES 



70-83 



grounded service conductor that has a rating or setting not 
higher than the allowable ampacity of the conductor. A set 
of fuses shall be considered all the fuses required to protect 
all the ungrounded conductors of a circuit. Single-pole cir- 
cuit breakers, grouped in accordance with 230.71(B), shall 
be considered as one protective device. 

Exception No. 1: For motor-starting currents, ratings that 
conform with 430.52, 430.62, and 430.63 shall be 
permitted. 

Exception No. 2: Fuses and circuit breakers with a rating 
or setting that conform with 240.4(B) or (C) and 240.6 
shall be permitted. 

Exception No. 3: Two to six circuit breakers or sets of fuses 
shall be permitted as the overcurrent device to provide the 
overload protection. The sum of the ratings of the circuit 
breakers or fuses shall be permitted to exceed the ampacity 
of the service conductors, provided the calculated load 
does not exceed the ampacity of the service conductors. 

Exception No. 4: Overload protection for fire pump supply 
conductors shall conform with 695.4(B)(1). 

Exception No. 5: Overload protection for 120/240-volt, 
3-wire, single-phase dwelling services shall be permitted in 
accordance with the requirements of 310.15(B)(6). 

(B) Not in Grounded Conductor. No overcurrent device 
shall be inserted in a grounded service conductor except a 
circuit breaker that simultaneously opens all conductors of 
the circuit. 

230.91 Location. The service overcurrent device shall be 
an integral part of the service disconnecting means or shall 
be located immediately adjacent thereto. 

230.92 Locked Service Overcurrent Devices. Where the 
service overcurrent devices are locked or sealed or are not 
readily accessible to the occupant, branch-circuit overcur- 
rent devices shall be installed on the load side, shall be 
mounted in a readily accessible location, and shall be of 
lower ampere rating than the service overcurrent device. 

230.93 Protection of Specific Circuits. Where necessary 
to prevent tampering, an automatic overcurrent device that 
protects service conductors supplying only a specific load, 
such as a water heater, shall be permitted to be locked or 
sealed where located so as to be accessible. 

230.94 Relative Location of Overcurrent Device and 
Other Service Equipment. The overcurrent device shall 
protect all circuits and devices. 

Exception No. 1: The service switch shall be permitted on 
the supply side. 



Exception No. 2: High-impedance shunt circuits, surge ar- 
resters, surge-protective capacitors, and instrument trans- 
formers (current and voltage) shall be permitted to be con- 
nected and installed on the supply side of the service 
disconnecting means as permitted in 230.82. 

Exception No. 3: Circuits for load management devices 
shall be permitted to be connected on the supply side of the 
service overcurrent device where separately provided with 
overcurrent protection. 

Exception No. 4: Circuits used only for the operation of 
fire alarm, other protective signaling systems, or the supply 
to fire pump equipment shall be permitted to be connected 
on the supply side of the service overcurrent device where 
separately provided with overcurrent protection. 

Exception No. 5: Meters nominally rated not in excess of 
600 volts, provided all metal housings and service enclo- 
sures are grounded in accordance with Article 250. 

Exception No. 6: Where service equipment is power oper- 
able, the control circuit shall be permitted to be connected 
ahead of the service equipment if suitable overcurrent pro- 
tection and disconnecting means are provided. 

230.95 Ground-Fault Protection of Equipment. Ground- 
fault protection of equipment shall be provided for solidly 
grounded wye electrical services of more than 150 volts to 
ground but not exceeding 600 volts phase-to-phase for each 
service disconnect rated 1000 amperes or more. 

The rating of the service disconnect shall be considered 
to be the rating of the largest fuse that can be installed or 
the highest continuous current trip setting for which the 
actual overcurrent device installed in a circuit breaker is 
rated or can be adjusted. 

Solidly Grounded — Definition. Connection of the 
grounded conductor to ground without inserting any resis- 
tor or impedance device. 

Exception No. 1: The ground-fault protection provisions of 
this section shall not apply to a service disconnect for a 
continuous industrial process where a nonorderly shutdown 
will introduce additional or increased hazards. 

Exception No. 2: The ground-fault protection provisions of 
this section shall not apply to fire pumps. 

(A) Setting. The ground-fault protection system shall op- 
erate to cause the service disconnect to open all un- 
grounded conductors of the faulted circuit. The maximum 
setting of the ground-fault protection shall be 1200 am- 
peres, and the maximum time delay shall be one second for 
ground-fault currents equal to or greater than 3000 am- 
peres. 

(B) Fuses. If a switch and fuse combination is used, the 
fuses employed shall be capable of interrupting any current 



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70-84 



ARTICLE 230 — SERVICES 



higher than the interrupting capacity of the switch during a 
time that the ground-fault protective system will not cause 
the switch to open. 

(C) Performance Testing. The ground-fault protection 
system shall be performance tested when first installed on 
site. The test shall be conducted in accordance with instruc- 
tions that shall be provided with the equipment. A written 
record of this test shall be made and shall be available to 
the authority having jurisdiction. 

FPN No. 1: Ground-fault protection that functions to open 
the service disconnect affords no protection from faults on 
the line side of the protective element. It serves only to 
limit damage to conductors and equipment on the load side 
in the event of an arcing ground fault on the load side of the 
protective element. 

FPN No. 2: This added protective equipment at the service 
equipment may make it necessary to review the overall 
wiring system for proper selective overcurrent protection 
coordination. Additional installations of ground-fault pro- 
tective equipment may be needed on feeders and branch 
circuits where maximum continuity of electrical service is 
necessary. 

FPN No. 3: Where ground- fault protection is provided for 
the service disconnect and interconnection is made with 
another supply system by a transfer device, means or de- 
vices may be needed to ensure proper ground-fault sensing 
by the ground-fault protection equipment. 



VIII. Services Exceeding 600 Volts, Nominal 

230.200 General. Service conductors and equipment used 
on circuits exceeding 600 volts, nominal, shall comply with 
all the applicable provisions of the preceding sections of 
this article and with the following sections, which supple- 
ment or modify the preceding sections. In no case shall the 
provisions of Part VIII apply to equipment on the supply 
side of the service point. 

FPN: For clearances of conductors of over 600 volts, 
nominal, see ANSI C2-1997, National Electrical Safety 
Code. 

230.202 Service-Entrance Conductors. Service-entrance 
conductors to buildings or enclosures shall be installed to 
conform to 230.202(A) and (B). 

(A) Conductor Size. Service-entrance conductors shall not 
be smaller than 6 AWG unless in multiconductor cable. 
Multiconductor cable shall not be smaller than 8 AWG. 

(B) Wiring Methods. Service-entrance conductors shall 
be installed by one of the wiring methods covered in 
300.37 and 300.50. 

230.204 Isolating Switches. 

(A) Where Required. Where oil switches or air, oil, 
vacuum, or sulfur hexafluoride circuit breakers constitute 



the service disconnecting means, an isolating switch with 
visible break contacts shall be installed on the supply side 
of the disconnecting means and all associated service 
equipment. 

Exception: An isolating switch shall not be required where 
the circuit breaker or switch is mounted on removable truck 
panels or metal-enclosed switchgear units, that 

(a) Cannot be opened unless the circuit is disconnected, 
and 

(b) Where all energized parts are automatically discon- 
nected when the circuit breaker or switch is removed 
from the normal operating position 

(B) Fuses as Isolating Switch. Where fuses are of the type 
that can be operated as a disconnecting switch, a set of such 
fuses shall be permitted as the isolating switch. 

(C) Accessible to Qualified Persons Only. The isolating 
switch shall be accessible to qualified persons only. 

(D) Grounding Connection. Isolating switches shall be 
provided with a means for readily connecting the load side 
conductors to ground when disconnected from the source of 
supply. 

A means for grounding the load side conductors shall 
not be required for any duplicate isolating switch installed 
and maintained by the electric supply company. 

230.205 Disconnecting Means. 

(A) Location. The service disconnecting means shall be 
located in accordance with 230.70. 

(B) Type. Each service disconnect shall simultaneously 
disconnect all ungrounded service conductors that it con- 
trols and shall have a fault-closing rating that is not less 
than the maximum short-circuit current available at its sup- 
ply terminals. 

Where fused switches or separately mounted fuses are 
installed, the fuse characteristics shall be permitted to con- 
tribute to the fault-closing rating of the disconnecting 
means. 

(C) Remote Control. For multibuilding, industrial instal- 
lations under single management, the service disconnecting 
means shall be permitted to be located at a separate build- 
ing or structure. In such cases, the service disconnecting 
means shall be permitted to be electrically operated by a 
readily accessible, remote-control device. 

230.206 Overcurrent Devices as Disconnecting Means. 

Where the circuit breaker or alternative for it, as specified 
in 230.208 for service overcurrent devices, meets the re- 
quirements specified in 230.205, they shall constitute the 
service disconnecting means. 



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ARTICLE 240 — OVERCURRENT PROTECTION 



70-85 



230.208 Protection Requirements. A short-circuit protec- 
tive device shall be provided on the load side of, or as an 
integral part of, the service disconnect, and shall protect all 
ungrounded conductors that it supplies. The protective de- 
vice shall be capable of detecting and interrupting all val- 
ues of current, in excess of its trip setting or melting point., 
that can occur at its location. A fuse rated in continuous 
amperes not to exceed three times the ampacity of the con- 
ductor, or a circuit breaker with a trip setting of not more 
than six times the ampacity of the conductors, shall be 
considered as providing the required short-circuit protec- 
tion. 

FPN: See Tables 310.67 through 310.86 for ampacities of 
conductors rated 2001 volts and above. 

Overcurrent devices shall conform to 230.208(A) and (B). 

(A) Equipment Type. Equipment used to protect service- 
entrance conductors shall meet the requirements of Article 
490, Part II. 

(B) Enclosed Overcurrent Devices. The restriction to 
80 percent of the rating for an enclosed overcurrent device 
for continuous loads shall not apply to overcurrent devices 
installed in systems operating at over 600 volts. 

230.209 Surge Arresters (Lightning Arresters). Surge 
arresters installed in accordance with the requirements of 
Article 280 shall be permitted on each ungrounded over- 
head service conductor. 

230.210 Service Equipment — General Provisions. 

Service equipment, including instrument transformers, shall 
conform to Article 490, Part I. 

230.211 Metal-Enclosed Switchgear. Metal-enclosed 
switchgear shall consist of a substantial metal structure and 
a sheet metal enclosure. Where installed over a combustible 
floor, suitable protection thereto shall be provided. 

230.212 Over 35,000 Volts. Where the voltage exceeds 
35,000 volts between conductors that enter a building, they 
shall terminate in a metal-enclosed switchgear compart- 
ment or a vault conforming to the requirements of 450.41 
through 450.48. 



ARTICLE 240 
Overcurrent Protection 



I. General 



240.1 Scope. Parts I through VII of this article provide the 
general requirements for overcurrent protection and over- 
current protective devices not more than 600 volts, nomi- 
nal. Part VIII covers overcurrent protection for those por- 
tions of supervised industrial installations operating at 
voltages of not more than 600 volts, nominal. Part IX cov- 
ers overcurrent protection over 600 volts, nominal. 

FPN: Overcurrent protection for conductors and equipment 
is provided to open the circuit if the current reaches a value 
that will cause an excessive or dangerous temperature in 
conductors or conductor insulation. See also 110.9 for re- 
quirements for interrupting ratings and 110.10 for require- 
ments for protection against fault currents. 

240.2 Definitions. 

Coordination. The proper localization of a fault condition 
to restrict outages to the equipment affected, accomplished 
by the choice of selective fault-protective devices. 

Current-Limiting Overcurrent Protective Device. A de- 
vice that, when interrupting currents in its current-limiting 
range, reduces the current flowing in the faulted circuit to a 
magnitude substantially less than that obtainable in the 
same circuit if the device were replaced with a solid con- 
ductor having comparable impedance. 

Supervised Industrial Installation. For the purposes of 
Part VIII, the industrial portions of a facility where all of 
the following conditions are met: 

(1) Conditions of maintenance and engineering supervision 
ensure that only qualified persons monitor and service 
the system. 

(2) The premises wiring system has 2500 kVA or greater of 
load used in industrial process(es), manufacturing ac- 
tivities, or both, as calculated in accordance with Ar- 
ticle 220. 

(3) The premises has at least one service that is more than 
150 volts to ground and more than 300 volts 
phase-to-phase. 

This definition excludes installations in buildings used 
by the industrial facility for offices, warehouses, garages, 
machine shops, and recreational facilities that are not an 
integral part of the industrial plant, substation, or control 
center. 

Tap Conductors. As used in this article, a tap conductor is 
defined as a conductor, other than a service conductor, that 
has overcurrent protection ahead of its point of supply that 



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70-86 



ARTICLE 240 — OVERCURRENT PROTECTION 



exceeds the value permitted for similar conductors that are 
protected as described elsewhere in 240.4. 

240.3 Other Articles. Equipment shall be protected against 
overcurrent in accordance with the article in this Code that 
covers the type of equipment specified in Table 240.3. 

Table 240.3 Other Articles 



Equipment 


Article 


Air-conditioning and refrigerating equipment 


440 


Appliances 


422 


Audio signal processing, amplification, and 


640 


reproduction equipment 




Branch circuits 


210 


Busways 


368 


Capacitors 


460 


Class 1, Class 2, and Class 3 remote-control, 


725 


signaling, and power-limited circuits 




Closed-loop and programmed power 


780 


distribution 




Cranes and hoists 


610 


Electric signs and outline lighting 


600 


Electric welders 


630 


Electrolytic cells 


668 


Elevators, dumbwaiters, escalators, moving 


620 


walks, wheelchair lifts, and stairway chair 




lifts 




Emergency systems 


700 


Fire alarm systems 


760 


Fire pumps 


695 


Fixed electric heating equipment for pipelines 


427 


and vessels 




Fixed electric space-heating equipment 


424 


Fixed outdoor electric deicing and 


426 


snow-melting equipment 




Generators 


445 


Health care facilities 


517 


Induction and dielectric heating equipment 


665 


Industrial machinery 


670 


Luminaires (lighting fixtures), lampholders, 


410 


and lamps 




Motion picture and television studios and 


530 


similar locations 




Motors, motor circuits, and controllers 


430 


Phase converters 


455 


Pipe organs 


650 


Places of assembly 


518 


Receptacles 


406 


Services 


230 


Solar photovoltaic systems 


690 


Switchboards and panelboards 


408 


Theaters, audience areas of motion picture and 


520 


television studios, and similar locations 




Transformers and transformer vaults 


450 


X-ray equipment 


660 



240.4 Protection of Conductors. Conductors, other than 
flexible cords, flexible cables, and fixture wires, shall be 
protected against overcurrent in accordance with their am- 



pacities specified in 310.15, unless otherwise permitted or 
required in 240.4(A) through (G). 

(A) Power Loss Hazard. Conductor overload protection 
shall not be required where the interruption of the circuit 
would create a hazard, such as in a material-handling mag- 
net circuit or fire pump circuit. Short-circuit protection 
shall be provided. 

FPN: See NFPA 20-1999, Standard for the Installation of 
Stationary Pumps for Fire Protection. 

(B) Devices Rated 800 Amperes or Less. The next higher 
standard overcurrent device rating (above the ampacity of 
the conductors being protected) shall be permitted to be 
used, provided all of the following conditions are met: 

(1) The conductors being protected are not part of a mul- 
tioutlet branch circuit supplying receptacles for cord- 
and-plug-connected portable loads. 

(2) The ampacity of the conductors does not correspond 
with the standard ampere rating of a fuse or a circuit 
breaker without overload trip adjustments above its rat- 
ing (but that shall be permitted to have other trip or 
rating adjustments). 

(3) The next higher standard rating selected does not ex- 
ceed 800 amperes. 

(C) Devices Rated Over 800 Amperes. Where the over- 
current device is rated over 800 amperes, the ampacity of 
the conductors it protects shall be equal to or greater than 
the rating of the overcurrent device defined in 240.6. 

(D) Small Conductors. Unless specifically permitted in 
240.4(E) through (G), the overcurrent protection shall not 
exceed 15 amperes for 14 AWG, 20 amperes for 12 AWG, 
and 30 amperes for 10 AWG copper; or 15 amperes for 12 
AWG and 25 amperes for 10 AWG aluminum and copper- 
clad aluminum after any correction factors for ambient tem- 
perature and number of conductors have been applied. 

(E) Tap Conductors. Tap conductors shall be permitted to 
be protected against overcurrent in accordance with 
210.19(A)(3) and (4), 240.5(B)(2), 240.21, 368.11, 368.12, 
and 430.53(D). 

(F) Transformer Secondary Conductors. Single-phase 
(other than 2-wire) and multiphase (other than delta-delta, 
3-wire) transformer secondary conductors shall not be con- 
sidered to be protected by the primary overcurrent protec- 
tive device. Conductors supplied by the secondary side of a 
single-phase transformer having a 2-wire (single-voltage) 



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• 



secondary, or a three-phase, delta-delta connected trans- 
former having a 3-wire (single-voltage) secondary, shall be 
permitted to be protected by overcurrent protection pro- 
vided on the primary (supply) side of the transformer, pro- 
vided this protection is in accordance with 450.3 and does 
not exceed the value determined by multiplying the second- 
ary conductor ampacity by the secondary to primary trans- 
former voltage ratio. 

(G) Overcurrent Protection for Specific Conductor 
Applications. Overcurrent protection for the specific con- 
ductors shall be permitted to be provided as referenced in 
Table 240.4(G). 

Table 240.4(G) Specific Conductor Applications 



Conductor 


Article 


Section 


Air-conditioning and 


440, 


Parts 




refrigeration equipment 


III, 1 


VI 




circuit conductors 








Capacitor circuit 


460 




460.8(B) and 


conductors 






460.25(A)-(D) 


Control and 


727 




727.9 


instrumentation circuit 








conductors (Type ITC) 








Electric welder circuit 


630 




630.12 and 


conductors 






630.32 


Fire alarm system circuit 


760 




760.23, 760.24, 


conductors 






760.41, and 
Chapter 9, Tables 
12(A) and 12(B) 


Motor-operated appliance 


422, 


Part II 




circuit conductors 








Motor and motor-control 


430, 


Parts 




circuit conductors 


in, IV, V, 






VI, 1 


VII 




Phase converter supply 


455 




455.7 


conductors 








Remote-control, signaling, 


725 




725.23, 725.24, 


and power- limited 






725.41, and 


circuit conductors 






Chapter 9, Tables 
11(A) and 11(B) 


Secondary tie conductors 


450 




450.6 



240.5 Protection of Flexible Cords, Flexible Cables, and 
Fixture Wires. Flexible cord and flexible cable, including 
tinsel cord and extension cords, and fixture wires shall be 
protected against overcurrent by either 240.5(A) or (B). 

(A) Ampacities. Flexible cord and flexible cable shall be 
protected by an overcurrent device in accordance with their 
ampacity as specified in Tables 400.5(A) and 400.5(B). Fix- 
ture wire shall be protected against overcurrent in accor- 
dance with its ampacity as specified in Table 402.5. Supple- 
mentary overcurrent protection, as in 240.10, shall be 
permitted to be an acceptable means for providing this pro- 
tection. 



(B) Branch Circuit Overcurrent Device. Flexible cord 
shall be protected where supplied by a branch circuit in 
accordance with one of the methods described in 
240.5(B)(1), (2), or (3). 

(1) Supply Cord of Listed Appliance or Portable 
Lamps. Where flexible cord or tinsel cord is approved for 
and used with a specific listed appliance or portable lamp, it 
shall be permitted to be supplied by a branch circuit of 
Article 210 in accordance with the following: 

(1) 20-ampere circuits — tinsel cord or 18 AWG cord and 
larger 

(2) 30-ampere circuits — 16 AWG cord and larger 

(3) 40-ampere circuits — cord of 20-ampere capacity and 
over 

(4) 50-ampere circuits — cord of 20-ampere capacity and 
over 

(2) Fixture Wire. Fixture wire shall be permitted to be 
tapped to the branch circuit conductor of a branch circuit of 
Article 210 in accordance with the following: 

(1) 20-ampere circuits — 18 AWG, up to 15 m (50 ft) of 
run length 

(2) 20-ampere circuits — 16 AWG, up to 30 m (100 ft) of 
run length 

(3) 20-ampere circuits — 14 AWG and larger 

(4) 30-ampere circuits — 14 AWG and larger 

(5) 40-ampere circuits — 12 AWG and larger 

(6) 50-ampere circuits — 12 AWG and larger 

(3) Extension Cord Sets. Flexible cord used in listed ex- 
tension cord sets, or in extension cords made with sepa- 
rately listed and installed components, shall be permitted to 
be supplied by a branch circuit of Article 210 in accordance 
with the following: 

20-ampere circuits — 16 AWG and larger 

240.6 Standard Ampere Ratings. 

(A) Fuses and Fixed-Trip Circuit Breakers. The stan- 
dard ampere ratings for fuses and inverse time circuit 
breakers shall be considered 15, 20, 25, 30, 35, 40, 45, 50, 
60, 70, 80, 90, 100, 110, 125, 150, 175, 200, 225, 250, 300, 
350, 400, 450, 500, 600, 700, 800, 1000, 1200, 1600, 2000, 
2500, 3000, 4000, 5000, and 6000 amperes. Additional 
standard ampere ratings for fuses shall be 1, 3, 6, 10, and 
601. The use of fuses and inverse time circuit breakers with 
nonstandard ampere ratings shall be permitted. 

(B) Adjustable-Trip Circuit Breakers. The rating of 
adjustable-trip circuit breakers having external means for 
adjusting the current setting (long-time pickup setting), not 
meeting the requirements of 240.6(C), shall be the maxi- 
mum setting possible. 



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ARTICLE 240 — OVERCURRENT PROTECTION 



(C) Restricted Access Adjustable-Trip Circuit Breakers. 

A circuit breaker(s) that has restricted access to the adjust- 
ing means shall be permitted to have an ampere rating(s) 
that is equal to the adjusted current setting (long-time 
pickup setting). Restricted access shall be defined as lo- 
cated behind one of the following: 

(1) Removable and sealable covers over the adjusting 
means 

(2) Bolted equipment enclosure doors 

(3) Locked doors accessible only to qualified personnel 

240.8 Fuses or Circuit Breakers in Parallel. Fuses and 
circuit breakers shall be permitted to be connected in par- 
allel where they are factory assembled in parallel and listed 
as a unit. Individual fuses, circuit breakers, or combinations 
thereof shall not otherwise be connected in parallel. 

240.9 Thermal Devices. Thermal relays and other devices 
not designed to open short circuits or ground faults shall 
not be used for the protection of conductors against over- 
current due to short circuits or ground faults, but the use of 
such devices shall be permitted to protect motor branch- 
circuit conductors from overload if protected in accordance 
with 430.40. 

240.10 Supplementary Overcurrent Protection. Where 
supplementary overcurrent protection is used for luminaires 
(lighting fixtures), appliances, and other equipment or for 
internal circuits and components of equipment, it shall not 
be used as a substitute for branch-circuit overcurrent de- 
vices or in place of the branch-circuit protection specified 
in Article 210. Supplementary overcurrent devices shall not 
be required to be readily accessible. 

240.12 Electrical System Coordination. Where an or- 
derly shutdown is required to minimize the hazard(s) to 
personnel and equipment, a system of coordination based 
on the following two conditions shall be permitted: 

(1) Coordinated short-circuit protection 

(2) Overload indication based on monitoring systems or 
devices 

FPN: The monitoring system may cause the condition to 
go to alarm, allowing corrective action or an orderly shut- 
down, thereby minimizing personnel hazard and equipment 
damage. 

240.13 Ground-Fault Protection of Equipment. 

Ground-fault protection of equipment shall be provided in 
accordance with the provisions of 230.95 for solidly 
grounded wye electrical systems of more than 150 volts to 
ground but not exceeding 600 volts phase-to-phase for each 
individual device used as a building or structure main dis- 
connecting means rated 1000 amperes or more. 



The provisions of this section shall not apply to the 
disconnecting means for the following: 

(1) Continuous industrial processes where a nonorderly 
shutdown will introduce additional or increased haz- 
ards 

(2) Installations where ground-fault protection is provided 
by other requirements for services or feeders 

(3) Fire pumps installed in accordance with Article 695 

II. Location 

240.20 Ungrounded Conductors. 

(A) Overcurrent Device Required. A fuse or an overcur- 
rent trip unit of a circuit breaker shall be connected in 
series with each ungrounded conductor. A combination of a 
current transformer and overcurrent relay shall be consid- 
ered equivalent to an overcurrent trip unit. 

FPN: For motor circuits, see Parts III, IV, V, and X of 
Article 430. 

(B) Circuit Breaker as Overcurrent Device. Circuit 
breakers shall open all ungrounded conductors of the circuit 
unless otherwise permitted in 240.20(B)(1), (B)(2), and 
(B)(3). 

(1) Multiwire Branch Circuit. Except where limited by 
210.4(B), individual single-pole circuit breakers, with or 
without approved handle ties, shall be permitted as the pro- 
tection for each ungrounded conductor of multiwire branch 
circuits that serve only single-phase line-to-neutral loads. 

(2) Grounded Single-Phase and 3-wire dc Circuits. In 

grounded systems, individual single-pole circuit breakers 
with approved handle ties shall be permitted as the protec- 
tion for each ungrounded conductor for line-to-line con- 
nected loads for single-phase circuits or 3-wire, direct- 
current circuits. 

(3) 3-Phase and 2-Phase Systems. For line-to-line loads 
in 4-wire, 3-phase systems or 5-wire, 2-phase systems hav- 
ing a grounded neutral and no conductor operating at a 
voltage greater than permitted in 210.6, individual single- 
pole circuit breakers with approved handle ties shall be 
permitted as the protection for each ungrounded conductor. 

(C) Closed-Loop Power Distribution Systems. Listed de- 
vices that provide equivalent overcurrent protection in 
closed-loop power distribution systems shall be permitted 
as a substitute for fuses or circuit breakers. 

240.21 Location in Circuit. Overcurrent protection shall 
be provided in each ungrounded circuit conductor and shall 
be located at the point where the conductors receive their 
supply except as specified in 240.21(A) through (G). No 



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ARTICLE 240 — OVERCURRENT PROTECTION 



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conductor supplied under the provisions of 240.21(A) 
through (G) shall supply another conductor under those 
provisions, except through an overcurrent protective device 
meeting the requirements of 240.4. 

(A) Branch-Circuit Conductors. Branch-circuit tap con- 
ductors meeting the requirements specified in 210.19 shall 
be permitted to have overcurrent protection located as 
specified in that section. 

(B) Feeder Taps. Conductors shall be permitted to be 
tapped, without overcurrent protection at the tap, to a 
feeder as specified in 240.21(B)(1) through (5). 

(1) Taps Not Over 3 m (10 ft) Long. Where the length of 
the tap conductors does not exceed 3 m (10 ft) and the tap 
conductors comply with all of the following: 

(1) The ampacity of the tap conductors is 

a. Not less than the combined computed loads on the 
circuits supplied by the tap conductors, and 

b. Not less than the rating of the device supplied by 
the tap conductors or not less than the rating of the 
overcurrent-protective device at the termination of 
the tap conductors. 

(2) The tap conductors do not extend beyond the switch- 
board, panelboard, disconnecting means, or control de- 
vices they supply. 

(3) Except at the point of connection to the feeder, the tap 
conductors are enclosed in a raceway, which shall ex- 
tend from the tap to the enclosure of an enclosed 
switchboard, panelboard, or control devices, or to the 
back of an open switchboard. 

(4) For field installations where the tap conductors leave 
the enclosure or vault in which the tap is made, the 
rating of the overcurrent device on the line side of the 
tap conductors shall not exceed 10 times the ampacity 
of the tap conductor. 

FPN: For overcurrent protection requirements for lighting 
and appliance branch-circuit panelboards and certain power 
panelboards, see 408.16(A), (B), and (E). 

(2) Taps Not Over 7.5 m (25 ft) Long. Where the length 
of the tap conductors does not exceed 7.5 m (25 ft) and the 
tap conductors comply with all the following: 

(1) The ampacity of the tap conductors is not less than 
one-third of the rating of the overcurrent device pro- 
tecting the feeder conductors. 

(2) The tap conductors terminate in a single circuit breaker 
or a single set of fuses that will limit the load to the 
ampacity of the tap conductors. This device shall be 
permitted to supply any number of additional overcur- 
rent devices on its load side. 

(3) The tap conductors are suitably protected from physical 
damage or are enclosed in a raceway. 



(3) Taps Supplying a Transformer [Primary Plus Sec- 
ondary Not Over 7.5 m (25 ft) Long]. Where the tap 
conductors supply a transformer and comply with all the 
following conditions: 

(1) The conductors supplying the primary of a transformer 
have an ampacity at least one-third the rating of the 
overcurrent device protecting the feeder conductors. 

(2) The conductors supplied by the secondary of the trans- 
former shall have an ampacity that, when multiplied by 
the ratio of the secondary-to-primary voltage, is at least 
one-third of the rating of the overcurrent device pro- 
tecting the feeder conductors. 

(3) The total length of one primary plus one secondary 
conductor, excluding any portion of the primary con- 
ductor that is protected at its ampacity, is not over 
7.5 m (25 ft). 

(4) The primary and secondary conductors are suitably 
protected from physical damage. 

(5) The secondary conductors terminate in a single circuit 
breaker or set of fuses that limit the load current to not 
more than the conductor ampacity that is permitted by 
310.15. 

(4) Taps Over 7.5 m (25 ft) Long. Where the feeder is in 
a high bay manufacturing building over 1 1 m (35 ft) high at 
walls and the installation complies with all the following 
conditions: 

(1) Conditions of maintenance and supervision ensure that 
only qualified persons service the systems. 

(2) The tap conductors are not over 7.5 m (25 ft) long 
horizontally and not over 30 m (100 ft) total length. 

(3) The ampacity of the tap conductors is not less than 
one-third the rating of the overcurrent device protecting 
the feeder conductors. 

(4) The tap conductors terminate at a single circuit breaker 
or a single set of fuses that limit the load to the ampac- 
ity of the tap conductors. This single overcurrent de- 
vice shall be permitted to supply any number of addi- 
tional overcurrent devices on its load side. 

(5) The tap conductors are suitably protected from physical 
damage or are enclosed in a raceway. 

(6) The tap conductors are continuous from end-to-end and 
contain no splices. 

(7) The tap conductors are sized 6 AWG copper or 4 AWG 
aluminum or larger. 

(8) The tap conductors do not penetrate walls, floors, or 
ceilings. 

(9) The tap is made no less than 9 m (30 ft) from the floor. 

(5) Outside Taps of Unlimited Length. Where the con- 
ductors are located outdoors of a building or structure, ex- 
cept at the point of load termination, and comply with all of 
the following conditions: 



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ARTICLE 240 — OVERCURRENT PROTECTION 



(1) The conductors are suitably protected from physical 
damage. 

(2) The conductors terminate at a single circuit breaker or 
a single set of fuses that limit the load to the ampacity 
of the conductors. This single overcurrent device shall 
be permitted to supply any number of additional over- 
current devices on its load side. 

(3) The overcurrent device for the conductors is an integral 
part of a disconnecting means or shall be located im- 
mediately adjacent thereto. 

(4) The disconnecting means for the conductors is installed 
at a readily accessible location complying with one of 
the following: 

a. Outside of a building or structure 

b. Inside, nearest the point of entrance of the conduc- 
tors 

c. Where installed in accordance with 230.6, nearest 
the point of entrance of the conductors 

(C) Transformer Secondary Conductors. Conductors 
shall be permitted to be connected to a transformer second- 
ary, without overcurrent protection at the secondary, as 
specified in 240.21(C)(1) through (6). 

FPN: For overcurrent protection requirements for trans- 
formers, see 450.3. 

(1) Protection by Primary Overcurrent Device. 

Conductors supplied by the secondary side of a single- 
phase transformer having a 2-wire (single-voltage) second- 
ary, or a three-phase, delta-delta connected transformer 
having a 3-wire (single-voltage) secondary, shall be permit- 
ted to be protected by overcurrent protection provided on 
the primary (supply) side of the transformer, provided this 
protection is in accordance with 450.3 and does not exceed 
the value determined by multiplying the secondary conduc- 
tor ampacity by the secondary to primary transformer volt- 
age ratio. 

Single-phase (other than 2-wire) and multiphase (other 
than delta-delta, 3-wire) transformer secondary conductors 
are not considered to be protected by the primary overcur- 
rent protective device. 

(2) Transformer Secondary Conductors Not Over 3 m 
(10 ft) Long. Where the length of secondary conductor 
does not exceed 3 m (10 ft) and complies with all of the 
following: 

(1) The ampacity of the secondary conductors is 

a. Not less than the combined computed loads on the 
circuits supplied by the secondary conductors, and 

b. Not less than the rating of the device supplied by 
the secondary conductors or not less than the rating 
of the overcurrent-protective device at the termina- 
tion of the secondary conductors 



(2) The secondary conductors do not extend beyond the 
switchboard, panelboard, disconnecting means, or con- 
trol devices they supply. 

(3) The secondary conductors are enclosed in a raceway, 
which shall extend from the transformer to the enclo- 
sure of an enclosed switchboard, panelboard, or control 
devices or to the back of an open switchboard. 

FPN: For overcurrent protection requirements for lighting 
and appliance branch-circuit panelboards and certain power 
panelboards, see 408.16(A), (B), and (E). 

(3) Industrial Installation Secondary Conductors Not 
Over 7.5 m (25 ft) Long. For industrial installations only, 
where the length of the secondary conductors does not ex- 
ceed 7.5 m (25 ft) and complies with all of the following: 

(1) The ampacity of the secondary conductors is not less 
than the secondary current rating of the transformer, 
and the sum of the ratings of the overcurrent devices 
does not exceed the ampacity of the secondary conduc- 
tors. 

(2) All overcurrent devices are grouped. 

(3) The secondary conductors are suitably protected from 
physical damage. 

(4) Outside Secondary of Building or Structure 
Conductors. Where the conductors are located outdoors of 
a building or structure, except at the point of load termina- 
tion, and comply with all of the following conditions: 

(1) The conductors are suitably protected from physical 
damage. 

(2) The conductors terminate at a single circuit breaker or 
a single set of fuses that limit the load to the ampacity 
of the conductors. This single overcurrent device shall 
be permitted to supply any number of additional over- 
current devices on its load side. 

(3) The overcurrent device for the conductors is an integral 
part of a disconnecting means or shall be located im- 
mediately adjacent thereto. 

(4) The disconnecting means for the conductors is installed 
at a readily accessible location complying with one of 
the following: 

a. Outside of a building or structure 

b. Inside, nearest the point of entrance of the conduc- 
tors 

c. Where installed in accordance with 230.6, nearest 
the point of entrance of the conductors 

(5) Secondary Conductors from a Feeder Tapped 
Transformer. Transformer secondary conductors installed 
in accordance with 240.21(B)(3) shall be permitted to have 
overcurrent protection as specified in that section. 

(6) Secondary Conductors Not Over 7.5 m (25 ft) Long. 

Where the length of secondary conductor does not exceed 
7.5 m (25 ft) and complies with all of the following: 



• 



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ARTICLE 240 — OVERCURRENT PROTECTION 



70-91 



(1) The secondary conductors shall have an ampacity that, 
when multiplied by the ratio of the secondary-to- 
primary voltage, is at least one-third of the rating of the 
overcurrent device protecting the primary of the trans- 
former. 

(2) The secondary conductors terminate in a single circuit 
breaker or set of fuses that limit the load current to not 
more than the conductor ampacity that is permitted by 
310.15. 

(3) The secondary conductors are suitably protected from 
physical damage. 

(D) Service Conductors. Service-entrance conductors 
shall be permitted to be protected by overcurrent devices in 
accordance with 230.91. 

(E) Busway Taps. Busways and busway taps shall be per- 
mitted to be protected against overcurrent in accordance 
with 368.10 through 368.13. 

(F) Motor Circuit Taps. Motor-feeder and branch-circuit 
conductors shall be permitted to be protected against over- 
current in accordance with 430.28 and 430.53, respectively. 

(G) Conductors from Generator Terminals. Conductors 
from generator terminals that meet the size requirement in 
445.13 shall be permitted to be protected against overload 
by the generator overload protective device(s) required by 
445.12. 

240.22 Grounded Conductor. No overcurrent device shall 
be connected in series with any conductor that is intention- 
ally grounded, unless one of the following two conditions is 
met: 

(1) The overcurrent device opens all conductors of the cir- 
cuit, including the grounded conductor, and is designed 
so that no pole can operate independently. 

(2) Where required by 430.36 or 430.37 for motor over- 
load protection. 

240.23 Change in Size of Grounded Conductor. Where a 
change occurs in the size of the ungrounded conductor, a 
similar change shall be permitted to be made in the size of 
the grounded conductor. 

240.24 Location in or on Premises. 

(A) Accessibility. Overcurrent devices shall be readily ac- 
cessible unless one of the following applies: 

(1) For busways, as provided in 368.12. 

(2) For supplementary overcurrent protection, as described 
in 240.10. 

(3) For overcurrent devices, as described in 225.40 and 
230.92. 



(4) For overcurrent devices adjacent to utilization equip- 
ment that they supply, access shall be permitted to be 
by portable means. 

(B) Occupancy. Each occupant shall have ready access to 
all overcurrent devices protecting the conductors supplying 
that occupancy. 

Exception No. 1: Where electric service and electrical 
maintenance are provided by the building management and 
where these are under continuous building management 
supervision, the service overcurrent devices and feeder 
overcurrent devices supplying more than one occupancy 
shall be permitted to be accessible to only authorized man- 
agement personnel in the following: 

(a) Multiple-occupancy buildings 

(b) Guest rooms of hotels and motels that are intended for 
transient occupancy 

Exception No. 2: Where electric service and electrical 
maintenance are provided by the building management and 
where these are under continuous building management 
supervision, the branch circuit overcurrent devices supply- 
ing any guest rooms shall be permitted to be accessible to 
only authorized management personnel for guest rooms of 
hotels and motels that are intended for transient occupancy. 

(C) Not Exposed to Physical Damage. Overcurrent de- 
vices shall be located where they will not be exposed to 
physical damage. 

FPN: See 110.11, Deteriorating Agents. 

(D) Not in Vicinity of Easily Ignitible Material. 

Overcurrent devices shall not be located in the vicinity of 
easily ignitible material, such as in clothes closets. 

(E) Not Located in Bathrooms. In dwelling units and 
guest rooms of hotels and motels, overcurrent devices, 
other than supplementary overcurrent protection, shall not 
be located in bathrooms as defined in Article 100. 

III. Enclosures 

240.30 General. 

(A) Protection from Physical Damage. Overcurrent de- 
vices shall be protected from physical damage by one of the 
following: 

(1) Installation in enclosures, cabinets, cutout boxes, or 
equipment assemblies 

(2) Mounting on open-type switchboards, panelboards, or 
control boards that are in rooms or enclosures free from 
dampness and easily ignitible material and are acces- 
sible only to qualified personnel 



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ARTICLE 240 — OVERCURRENT PROTECTION 



(B) Operating Handle. The operating handle of a circuit 
breaker shall be permitted to be accessible without opening 
a door or cover. 

240.32 Damp or Wet Locations. Enclosures for overcur- 
rent devices in damp or wet locations shall comply with 

312.2(A). 

240.33 Vertical Position. Enclosures for overcurrent de- 
vices shall be mounted in a vertical position unless that is 
shown to be impracticable. Circuit breaker enclosures shall 
be permitted to be installed horizontally where the circuit 
breaker is installed in accordance with 240.81. Listed 
busway plug-in units shall be permitted to be mounted in 
orientations corresponding to the busway mounting posi- 
tion. 

IV. Disconnecting and Guarding 

240.40 Disconnecting Means for Fuses. A disconnecting 
means shall be provided on the supply side of all fuses in 
circuits over 150 volts to ground and cartridge fuses in 
circuits of any voltage where accessible to other than quali- 
fied persons so that each individual circuit containing fuses 
can be independently disconnected from the source of 
power. A current-limiting device without a disconnecting 
means shall be permitted on the supply side of the service 
disconnecting means as permitted by 230.82. A single dis- 
connecting means shall be permitted on the supply side of 
more than one set of fuses as permitted by 430.112, Excep- 
tion, for group operation of motors and 424.22(C) for fixed 
electric space-heating equipment. 

240.41 Arcing or Suddenly Moving Parts. Arcing or sud- 
denly moving parts shall comply with 240.41(A) and (B). 

(A) Location. Fuses and circuit breakers shall be located 
or shielded so that persons will not be burned or otherwise 
injured by their operation. 

(B) Suddenly Moving Parts. Handles or levers of circuit 
breakers, and similar parts that may move suddenly in such 
a way that persons in the vicinity are likely to be injured by 
being struck by them, shall be guarded or isolated. 

V. Plug Fuses, Fuseholders, and Adapters 

240.50 General. 

(A) Maximum Voltage. Plug fuses shall be permitted to 
be used in the following circuits: 

(1) Circuits not exceeding 125 volts between conductors 

(2) Circuits supplied by a system having a grounded neu- 
tral where the line-to-neutral voltage does not exceed 
150 volts 



(B) Marking. Each fuse, fuseholder, and adapter shall be 
marked with its ampere rating. 

(C) Hexagonal Configuration. Plug fuses of 15-ampere 
and lower rating shall be identified by a hexagonal configu- 
ration of the window, cap, or other prominent part to dis- 
tinguish them from fuses of higher ampere ratings. 

(D) No Energized Parts. Plug fuses, fuseholders, and 
adapters shall have no exposed energized parts after fuses 
or fuses and adapters have been installed. 

(E) Screw Shell. The screw shell of a plug-type fuseholder 
shall be connected to the load side of the circuit. 

240.51 Edison-Base Fuses. 

(A) Classification. Plug fuses of the Edison-base type 
shall be classified at not over 125 volts and 30 amperes and 
below. 

(B) Replacement Only. Plug fuses of the Edison-base type 
shall be used only for replacements in existing installations 
where there is no evidence of overfusing or tampering. 

240.52 Edison-Base Fuseholders. Fuseholders of the 
Edison-base type shall be installed only where they are 
made to accept Type S fuses by the use of adapters. 

240.53 Type S Fuses. Type S fuses shall be of the plug 
type and shall comply with 240.53(A) and (B). 

(A) Classification. Type S fuses shall be classified at not 
over 125 volts and to 15 amperes, 16 to 20 amperes, and 
21 to 30 amperes. 

(B) Noninterchangeable. Type S fuses of an ampere clas- 
sification as specified in 240.53(A) shall not be inter- 
changeable with a lower ampere classification. They 
shall be designed so that they cannot be used in any fuse- 
holder other than a Type S fuseholder or a fuseholder with 
a Type S adapter inserted. 

240.54 Type S Fuses, Adapters, and Fuseholders. 

(A) To Fit Edison-Base Fuseholders. Type S adapters 
shall fit Edison-base fuseholders. 

(B) To Fit Type S Fuses Only. Type S fuseholders and 
adapters shall be designed so that either the fuseholder it- 
self or the fuseholder with a Type S adapter inserted cannot 
be used for any fuse other than a Type S fuse. 

(C) Nonremovable. Type S adapters shall be designed so 
that once inserted in a fuseholder, they cannot be removed. 



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ARTICLE 240 — OVERCURRENT PROTECTION 



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• 



(D) Nontamperable. Type S fuses, fuseholders, and adapt- 
ers shall be designed so that tampering or shunting (bridg- 
ing) would be difficult. 

(E) Interchangeability. Dimensions of Type S fuses, fuse- 
holders, and adapters shall be standardized to permit inter- 
changeability regardless of the manufacturer. 

VI. Cartridge Fuses and Fuseholders 

240.60 General. 

(A) Maximum Voltage — 300- Volt Type. Cartridge fuses 
and fuseholders of the 300-volt type shall be permitted to 
be used in the following circuits: 

(1) Circuits not exceeding 300 volts between conductors 

(2) Single-phase line-to-neutral circuits supplied from a 
3 -phase, 4- wire, solidly grounded neutral source where 
the line-to-neutral voltage does not exceed 300 volts 

(B) Noninterchangeable — 0-6000-Ampere Cartridge 
Fuseholders. Fuseholders shall be designed so that it will 
be difficult to put a fuse of any given class into a fuseholder 
that is designed for a current lower, or voltage higher, than 
that of the class to which the fuse belongs. Fuseholders for 
current-limiting fuses shall not permit insertion of fuses 
that are not current-limiting. 

(C) Marking. Fuses shall be plainly marked, either by 
printing on the fuse barrel or by a label attached to the 
barrel showing the following: 

(1) Ampere rating 

(2) Voltage rating 

(3) Interrupting rating where other than 10,000 amperes 

(4) Current limiting where applicable 

(5) The name or trademark of the manufacturer 

The interrupting rating shall not be required to be 
marked on fuses used for supplementary protection. 

240.61 Classification. Cartridge fuses and fuseholders 
shall be classified according to voltage and amperage 
ranges. Fuses rated 600 volts, nominal, or less shall be 
permitted to be used for voltages at or below their ratings. 

VII. Circuit Breakers 

240.80 Method of Operation. Circuit breakers shall be 
trip free and capable of being closed and opened by manual 
operation. Their normal method of operation by other than 
manual means, such as electrical or pneumatic, shall be 
permitted if means for manual operation are also provided. 

240.81 Indicating. Circuit breakers shall clearly indicate 
whether they are in the open "off' or closed "on" position. 



Where circuit breaker handles are operated vertically 
rather than rotationally or horizontally, the "up" position of 
the handle shall be the "on" position. 



240.82 Nontamperable. A circuit breaker shall be of such 
design that any alteration of its trip point (calibration) or the 
time required for its operation requires dismantling of the de- 
vice or breaking of a seal for other than intended adjustments. 

240.83 Marking. 

(A) Durable and Visible. Circuit breakers shall be marked 
with their ampere rating in a manner that will be durable 
and visible after installation. Such marking shall be permit- 
ted to be made visible by removal of a trim or cover. 

(B) Location. Circuit breakers rated at 100 amperes or less 
and 600 volts or less shall have the ampere rating molded, 
stamped, etched, or similarly marked into their handles or 
escutcheon areas. 

(C) Interrupting Rating. Every circuit breaker having an 
interrupting rating other than 5000 amperes shall have its 
interrupting rating shown on the circuit breaker. The inter- 
rupting rating shall not be required to be marked on circuit 
breakers used for supplementary protection. 

(D) Used as Switches. Circuit breakers used as switches in 
120- volt and 277-volt fluorescent lighting circuits shall be 
listed and shall be marked SWD or HID. Circuit breakers 
used as switches in high-intensity discharge lighting cir- 
cuits shall be listed and shall be marked as HID. 

(E) Voltage Marking. Circuit breakers shall be marked 
with a voltage rating not less than the nominal system volt- 
age that is indicative of their capability to interrupt fault 
currents between phases or phase to ground. 

240.85 Applications. A circuit breaker with a straight volt- 
age rating, such as 240V or 480V, shall be permitted to be 
applied in a circuit in which the nominal voltage between 
any two conductors does not exceed the circuit breaker's 
voltage rating. A two-pole circuit breaker shall not be used 
for protecting a 3-phase, corner-grounded delta circuit un- 
less the circuit breaker is marked 1 cj> — 3c}> to indicate such 
suitability. 

A circuit breaker with a slash rating, such as 120/240V 
or 480Y/277V, shall be permitted to be applied in a solidly 
grounded circuit where the nominal voltage of any conduc- 
tor to ground does not exceed the lower of the two values 
of the circuit breaker's voltage rating and the nominal volt- 
age between any two conductors does not exceed the higher 
value of the circuit breaker's voltage rating. 

FPN: Proper application of molded case circuit breakers on 
3-phase systems, other than solidly grounded wye, particu- 



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ARTICLE 240 — OVERCURRENT PROTECTION 



larly on corner grounded delta systems, considers the cir- 
cuit breakers' individual pole-interrupting capability. 

240.86 Series Ratings. Where a circuit breaker is used on 
a circuit having an available fault current higher than its 
marked interrupting rating by being connected on the load 
side of an acceptable overcurrent protective device having 
the higher rating, 240.86(A) and (B) shall apply. 

(A) Marking. The additional series combination interrupt- 
ing rating shall be marked on the end use equipment, such 
as switchboards and panelboards. 

(B) Motor Contribution. Series ratings shall not be used 
where 

(1) Motors are connected on the load side of the higher- 
rated overcurrent device and on the line side of the 
lower-rated overcurrent device, and 

(2) The sum of the motor full-load currents exceeds 1 per- 
cent of the interrupting rating of the lower-rated circuit 
breaker. 



VIII. Supervised Industrial Installations 

240.90 General. Overcurrent protection in areas of super- 
vised industrial installations shall comply with all of the 
other applicable provisions of this article, except as pro- 
vided in Part VIII. The provisions of Part VIII shall only be 
permitted to apply to those portions of the electrical system 
in the supervised industrial installation used exclusively for 
manufacturing or process control activities. 

240.92 Location in Circuit. An overcurrent device shall 
be connected in each ungrounded circuit conductor as re- 
quired in 240.92(A) through (D). 

(A) Feeder and Branch-Circuit Conductors. Feeder and 
branch-circuit conductors shall be protected at the point the 
conductors receive their supply as permitted in 240.21 or as 
otherwise permitted in 240.92(B), (C), or (D). 

(B) Transformer Secondary Conductors of Separately 
Derived Systems. Conductors shall be permitted to be con- 
nected to a transformer secondary of a separately derived 
system, without overcurrent protection at the connection, 
where the conditions of 240.92(B)(1), (2), and (3) are met. 

(1) Short-Circuit and Ground-Fault Protection. The 

conductors shall be protected from short-circuit and 
ground-fault conditions by complying with one of the fol- 
lowing conditions: 

(1) The length of the secondary conductors does not ex- 
ceed 30 m (100 ft) and the transformer primary over- 
current device has a rating or setting that does not ex- 
ceed 150 percent of the value determined by 



multiplying the secondary conductor ampacity by the 
secondary-to-primary transformer voltage ratio. 

(2) The conductors are protected by a differential relay 
with a trip setting equal to or less than the conductor 
ampacity. 

(3) The conductors shall be considered to be protected if 
calculations, made under engineering supervision, de- 
termine that the system overcurrent devices will protect 
the conductors within recognized time vs. current limits 
for all short-circuit and ground-fault conditions. 

(2) Overload Protection. The conductors shall be pro- 
tected against overload conditions by complying with one 
of the following: 

(1) The conductors terminate in a single overcurrent device 
that will limit the load to the conductor ampacity. 

(2) The sum of the overcurrent devices at the conductor 
termination limits the load to the conductor ampacity. 
The overcurrent devices shall consist of not more than 
six circuit breakers or sets of fuses, mounted in a single 
enclosure, in a group of separate enclosures, or in or on 
a switchboard. There shall be no more than six over- 
current devices grouped in any one location. 

(3) Overcurrent relaying is connected [with a current trans- 
formers), if needed] to sense all of the secondary con- 
ductor current and limit the load to the conductor am- 
pacity by opening upstream or downstream devices. 

(4) Conductors shall be considered to be protected if cal- 
culations, made under engineering supervision, deter- 
mine that the system overcurrent devices will protect 
the conductors from overload conditions. 

(3) Physical Protection. The secondary conductors shall 
be suitably protected from physical damage. 

(C) Outside Feeder Taps. Outside conductors shall be 
permitted to be tapped to a feeder or to be connected at a 
transformer secondary, without overcurrent protection at 
the tap or connection, where all the following conditions 
are met: 

(1) The conductors are suitably protected from physical 
damage. 

(2) The sum of the overcurrent devices at the conductor 
termination limits the load to the conductor ampacity. 
The overcurrent devices shall consist of not more than 
six circuit breakers or sets of fuses mounted in a single 
enclosure, in a group of separate enclosures, or in or on 
a switchboard. There shall be no more than six over- 
current devices grouped in any one location. 

(3) The tap conductors are installed outdoors of a building 
or structure except at the point of load termination. 

(4) The overcurrent device for the conductors is an integral 
part of a disconnecting means or shall be located im- 
mediately adjacent thereto. 



• 



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ARTICLE 250 — GROUNDING 



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(5) The disconnecting means for the conductors is installed 
at a readily accessible location complying with one of 
the following: 

a. Outside of a building or structure 

b. Inside, nearest the point of entrance of the conduc- 
tors 

c. Where installed in accordance with 230.6, nearest 
the point of entrance of the conductors 

(D) Protection by Primary Overcurrent Device. 

Conductors supplied by the secondary side of a transformer 
shall be permitted to be protected by overcurrent protection 
provided on the primary (supply) side of the transformer, 
provided the primary device time-current protection char- 
acteristic, multiplied by the maximum effective primary-to- 
secondary transformer voltage ratio, effectively protects the 
secondary conductors. 

IX. Overcurrent Protection Over 600 Volts, Nominal 
240.100 Feeders and Branch Circuits. 

(A) Location and Type of Protection. Feeder and branch- 
circuit conductors shall have overcurrent protection in each 
ungrounded conductor located at the point where the con- 
ductor receives its supply or at an alternative location in the 
circuit when designed under engineering supervision that 
includes but is not limited to considering the appropriate 
fault studies and time-current coordination analysis of the 
protective devices and the conductor damage curves. The 
overcurrent protection shall be permitted to be provided by 
either 240.100(A)(1) or (A)(2). 

(1) Overcurrent Relays and Current Transformers. 

Circuit breakers used for overcurrent protection of 3-phase 
circuits shall have a minimum of three overcurrent relay 
elements operated from three current transformers. The 
separate overcurrent relay elements (or protective func- 
tions) shall be permitted to be part of a single electronic 
protective relay unit. 

On 3-phase, 3-wire circuits, an overcurrent relay ele- 
ment in the residual circuit of the current transformers shall 
be permitted to replace one of the phase relay elements. 

An overcurrent relay element, operated from a current 
transformer that links all phases of a 3-phase, 3-wire cir- 
cuit, shall be permitted to replace the residual relay element 
and one of the phase-conductor current transformers. 
Where the neutral is not regrounded on the load side of the 
circuit as permitted in 250.184(B), the current transformer 
shall be permitted to link all 3-phase conductors and the 
grounded circuit conductor (neutral). 

(2) Fuses. A fuse shall be connected in series with each 
ungrounded conductor. 

(B) Protective Devices. The protective device(s) shall be 
capable of detecting and interrupting all values of current 



that can occur at their location in excess of their trip-setting 
or melting point. 

(C) Conductor Protection. The operating time of the pro- 
tective device, the available short-circuit current, and the 
conductor used shall be coordinated to prevent damaging or 
dangerous temperatures in conductors or conductor insula- 
tion under short-circuit conditions. 

240.101 Additional Requirements for Feeders. 

(A) Rating or Setting of Overcurrent Protective 

Devices. The continuous ampere rating of a fuse shall not 
exceed three times the ampacity of the conductors. The 
long-time trip element setting of a breaker or the minimum 
trip setting of an electronically actuated fuse shall not ex- 
ceed six times the ampacity of the conductor. For fire 
pumps, conductors shall be permitted to be protected for 
overcurrent in accordance with 695.4(B). 

(B) Feeder Taps. Conductors tapped to a feeder shall be 
permitted to be protected by the feeder overcurrent device 
where that overcurrent device also protects the tap conduc- 
tor. 



ARTICLE 250 
Grounding 

I. General 

250.1 Scope. This article covers general requirements for 
grounding and bonding of electrical installations, and spe- 
cific requirements in (1) through (6). 

(1) Systems, circuits, and equipment required, permitted, 
or not permitted to be grounded 

(2) Circuit conductor to be grounded on grounded systems 

(3) Location of grounding connections 

(4) Types and sizes of grounding and bonding conductors 
and electrodes 

(5) Methods of grounding and bonding 

(6) Conditions under which guards, isolation, or insulation 
may be substituted for grounding 

250.2 Definitions. 

Effective Ground-Fault Current Path. An intentionally 
constructed, permanent, low-impedance electrically con- 
ductive path designed and intended to carry current under 
ground-fault conditions from the point of a ground fault on 
a wiring system to the electrical supply source. 

Ground Fault. An unintentional, electrically conducting con- 
nection between an ungrounded conductor of an electrical 



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ARTICLE 250 — GROUNDING 



circuit and the normally non-current-carrying conductors, me- 
tallic enclosures, metallic raceways, metallic equipment, or 
earth. 

Ground-Fault Current Path. An electrically conductive 
path from the point of a ground fault on a wiring system 
through normally non-current-carrying conductors, equip- 
ment, or the earth to the electrical supply source. 

FPN: Examples of ground-fault current paths could consist 
of any combination of equipment grounding conductors, 
metallic raceways, metallic cable sheaths, electrical equip- 
ment, and any other electrically conductive material such as 
metal water and gas piping, steel framing members, stucco 
mesh, metal ducting, reinforcing steel, shields of commu- 
nications cables, and the earth itself. 

250.3 Application of Other Articles. In other articles ap- 
plying to particular cases of installation of conductors and 
equipment, there are requirements identified in Table 250.3 
that are in addition to, or modifications of, those of this 
article. 



Table 250.3 Additional Grounding Requirements 



Conductor/Equipment Article 



Section 



Agricultural buildings 
Audio signal processing, 

amplification, and 

reproduction equipment 
Branch circuits 
Cablebus 
Capacitors 
Circuits and equipment 720 

operating at less than 50 

volts 
Class 1, Class 2, and Class 

3 remote-control, 

signaling, and 

power-limited circuits 
Closed-loop and 

programmed power 

distribution 
Communications circuits 800 

Community antenna 

television and radio 

distribution systems 
Conductors for general 310 

wiring 
Cranes and hoists 610 

Electrically driven or 

controlled irrigation 

machines 
Electric signs and outline 600 

lighting 
Electrolytic cells 668 

Elevators, dumbwaiters, 620 

escalators, moving 

walks, wheelchair lifts, 

and stairway chair lifts 



547.9 and 547.10 
640.7 



210.5, 210.6, 406.3 

370.9 

460.10, 460.27 



725.9 



780.3 



820.33, 820.40, 
820.41 



675.11(C), 675.12, 

675.13, 675.14, 

675.15 



Table 250.3 Continued 



Conductor/Equipment Article 



Fire alarm systems 
Fixed electric heating 

equipment for pipelines 

and vessels 
Fixed outdoor electric 

deicing and 

snow-melting equipment 
Flexible cords and cables 
Floating buildings 

Grounding-type 

receptacles, adapters, 

cord connectors, and 

attachment plugs 
Hazardous (classified) 

locations 
Health care facilities 
Induction and dielectric 

heating equipment 
Industrial machinery 
Information technology 

equipment 
Intrinsically safe systems 
Luminaires (lighting 

fixtures) and lighting 

equipment 
Luminaires (fixtures), 

lampholders, lamps, and 

receptacles 
Marinas and boatyards 
Mobile homes and mobile 

home park 
Motion picture and 

television studios and 

similar locations 
Motors, motor circuits, 

and controllers 
Outlet, device, pull and 

junction boxes, conduit 

bodies and fittings 
Over 600 volts, nominal, 

underground wiring 

methods 
Panelboards 
Pipe organs 
Radio and television 

equipment 
Receptacles and cord 

connectors 
Recreational vehicles and 

recreational vehicle 

parks 
Services 
Solar photovoltaic systems 



Swimming pools, 
fountains, and similar 
installations 



500-517 

517 
665 

670 



410 



550 



430 



650 
810 



551 



230 



680 



Section 



760.9 

427.29, 427.48 



426.27 



400.22, 400.23 

553.8, 553.10, 

553.11 

406.9 



645.15 

504.50 

410.17,410.18, 

410.20, 410.21, 

410.105(B) 



555.15 
530.20, 530.66 

314.4, 314.25 

300.50(B) 

408.20 

406.3 



690.41, 690.42, 
690.43, 
690.45, 
690.47 



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ARTICLE 250 — GROUNDING 



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Table 250.3 Continued 



Conductor/Equipment Article 



Section 



Switchboards and 

panelboards 
Switches 
Theaters, audience areas of 

motion picture and 

television studios, and 

similar locations 
Transformers and 

transformer vaults 
Use and identification of 

grounded conductors 
X-ray equipment 



200 
660 



408.3(D) 

404.12 
520.81 



450.10 



517.78 



250.4 General Requirements for Grounding and 
Bonding. The following general requirements identify 
what grounding and bonding of electrical systems are re- 
quired to accomplish. The prescriptive methods contained 
in Article 250 shall be followed to comply with the perfor- 
mance requirements of this section. 

(A) Grounded Systems. 

(1) Electrical System Grounding. Electrical systems that 
are grounded shall be connected to earth in a manner that 
will limit the voltage imposed by lightning, line surges, or 
unintentional contact with higher- voltage lines and that will 
stabilize the voltage to earth during normal operation. 

(2) Grounding of Electrical Equipment. Non-current- 
carrying conductive materials enclosing electrical conduc- 
tors or equipment, or forming part of such equipment, shall 
be connected to earth so as to limit the voltage to ground on 
these materials. 

(3) Bonding of Electrical Equipment. Non-current- 
carrying conductive materials enclosing electrical conduc- 
tors or equipment, or forming part of such equipment, shall 
be connected together and to the electrical supply source in 
a manner that establishes an effective ground-fault current 
path. 

(4) Bonding of Electrically Conductive Materials and 
Other Equipment. Electrically conductive materials that 
are likely to become energized shall be connected together 
and to the electrical supply source in a manner that estab- 
lishes an effective ground-fault current path. 

(5) Effective Ground-Fault Current Path. Electrical 
equipment and wiring and other electrically conductive ma- 
terial likely to become energized shall be installed in a 
manner that creates a permanent, low-impedance circuit 
capable of safely carrying the maximum ground-fault cur- 
rent likely to be imposed on it from any point on the wiring 
system where a ground fault may occur to the electrical 



supply source. The earth shall not be used as the sole equip- 
ment grounding conductor or effective ground-fault current 
path. 

(B) Ungrounded Systems. 

(1) Grounding Electrical Equipment. Non-current- 
carrying conductive materials enclosing electrical conduc- 
tors or equipment, or forming part of such equipment, shall 
be connected to earth in a manner that will limit the voltage 
imposed by lightning or unintentional contact with higher- 
voltage lines and limit the voltage to ground on these ma- 
terials. 

(2) Bonding of Electrical Equipment. Non-current- 
carrying conductive materials enclosing electrical conduc- 
tors or equipment, or forming part of such equipment, shall 
be connected together and to the supply system grounded 
equipment in a manner that creates a permanent, low- 
impedance path for ground-fault current that is capable of 
carrying the maximum fault current likely to be imposed on 
it. 

(3) Bonding of Electrically Conductive Materials and 
Other Equipment. Electrically conductive materials that 
are likely to become energized shall be connected together 
and to the supply system grounded equipment in a manner 
that creates a permanent, low-impedance path for ground- 
fault current that is capable of carrying the maximum fault 
current likely to be imposed on it. 

(4) Path for Fault Current. Electrical equipment, wiring, 
and other electrically conductive material likely to become 
energized shall be installed in a manner that creates a per- 
manent, low-impedance circuit from any point on the wir- 
ing system to the electrical supply source to facilitate the 
operation of overcurrent devices should a second fault oc- 
cur on the wiring system. The earth shall not be used as the 
sole equipment grounding conductor or effective fault- 
current path. 

FPN No. 1: A second fault that occurs through the equip- 
ment enclosures and bonding is considered a ground fault. 

FPN No. 2: See Figure 250.4 for information on the orga- 
nization of Article 250. 

250.6 Objectionable Current over Grounding Conduc- 
tors. 

(A) Arrangement to Prevent Objectionable Current. 

The grounding of electrical systems, circuit conductors, 
surge arresters, and conductive non-current-carrying mate- 
rials and equipment shall be installed and arranged in a 
manner that will prevent objectionable current over the 
grounding conductors or grounding paths. 



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ARTICLE 250 — GROUNDING 



Part I General 



Part II Circuit and 
system grounding 



Part VIII Direct-current 
systems 



Part X Grounding of 

systems and circuits of 

1 kV and over (high voltage) 



Part III Grounding electrode 

system and grounding 

electrode conductor 



Part IV Enclosure, 

raceway, and service 

cable grounding 



Part VI Equipment 

grounding and equipment 

grounding conductors 




Part V Bonding 



Part VII Methods of 
equipment grounding 



Part IX Instruments, 
meters, and relays 



Figure 250.4 Grounding. 

(B) Alterations to Stop Objectionable Current. If the 

use of multiple grounding connections results in objection- 
able current, one or more of the following alterations shall 
be permitted to be made, provided that the requirements of 
250.4(A)(5) or 250.4(B)(4) are met: 

(1) Discontinue one or more but not all of such grounding 
connections. 

(2) Change the locations of the grounding connections. 

(3) Interrupt the continuity of the conductor or conductive 
path interconnecting the grounding connections. 

(4) Take other suitable remedial and approved action. 

(C) Temporary Currents Not Classified as Objection- 
able Currents. Temporary currents resulting from acciden- 
tal conditions, such as ground-fault currents, that occur 
only while the grounding conductors are performing their 
intended protective functions shall not be classified as ob- 
jectionable current for the purposes specified in 250.6(A) 
and (B). 

(D) Limitations to Permissible Alterations. The provi- 
sions of this section shall not be considered as permitting 
electronic equipment from being operated on ac systems or 



branch circuits that are not grounded as required by this 
article. Currents that introduce noise or data errors in elec- 
tronic equipment shall not be considered the objectionable 
currents addressed in this section. 

(E) Isolation of Objectionable Direct-Current Ground 
Currents. Where isolation of objectionable dc ground cur- 
rents from cathodic protection systems is required, a listed 
ac coupling/dc isolating device shall be permitted in the 
equipment grounding path to provide an effective return 
path for ac ground-fault current while blocking dc current. 

250.8 Connection of Grounding and Bonding 
Equipment. Grounding conductors and bonding jumpers 
shall be connected by exothermic welding, listed pressure 
connectors, listed clamps, or other listed means. Connec- 
tion devices or fittings that depend solely on solder shall 
not be used. Sheet metal screws shall not be used to con- 
nect grounding conductors to enclosures. 

250.10 Protection of Ground Clamps and Fittings. 

Ground clamps or other fittings shall be approved for gen- 
eral use without protection or shall be protected from 
physical damage as indicated in (1) or (2). 

(1) In installations where they are not likely to be damaged 

(2) Where enclosed in metal, wood, or equivalent protec- 
tive covering 

250.12 Clean Surfaces. Nonconductive coatings (such as 
paint, lacquer, and enamel) on equipment to be grounded 
shall be removed from threads and other contact surfaces to 
ensure good electrical continuity or be connected by means 
of fittings designed so as to make such removal unneces- 
sary. 

II. Circuit and System Grounding 

250.20 Alternating-Current Circuits and Systems to Be 
Grounded. Alternating-current circuits and systems shall 
be grounded as provided for in 250.20(A), (B), (C), or (D). 
Other circuits and systems shall be permitted to be 
grounded. If such systems are grounded, they shall comply 
with the applicable provisions of this article. 

FPN: An example of a system permitted to be grounded is 
a coiner- grounded delta transformer connection. See 
250.26(4) for conductor to be grounded. 

(A) Alternating-Current Circuits of Less Than 50 Volts. 

Alternating-current circuits of less than 50 volts shall be 
grounded under any of the following conditions: 

(1) Where supplied by transformers, if the transformer sup- 
ply system exceeds 150 volts to ground 



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ARTICLE 250 — GROUNDING 



70-99 



(2) Where supplied by transformers, if the transformer sup- 
ply system is ungrounded 

(3) Where installed as overhead conductors outside of 
buildings 

(B) Alternating-Current Systems of 50 Volts to 1000 
Volts. Alternating-current systems of 50 volts to 1000 volts 
that supply premises wiring and premises wiring systems 
shall be grounded under any of the following conditions: 

(1) Where the system can be grounded so that the maxi- 
mum voltage to ground on the ungrounded conductors 
does not exceed 150 volts 

(2) Where the system is 3-phase, 4-wire, wye connected in 
which the neutral is used as a circuit conductor 

(3) Where the system is 3-phase, 4-wire, delta connected in 
which the midpoint of one phase winding is used as a 
circuit conductor 

(C) Alternating-Current Systems of 1 kV and Over. 

Alternating-current systems supplying mobile or portable 
equipment shall be grounded as specified in 250.188. 
Where supplying other than mobile or portable equipment, 
such systems shall be permitted to be grounded. 

(D) Separately Derived Systems. Separately derived sys- 
tems, as covered in 250.20(A) or (B), shall be grounded as 
specified in 250.30. 

FPN No. 1: An alternate ac power source such as an on- 
site generator is not a separately derived system if the neu- 
tral is solidly interconnected to a service-supplied system 
neutral. 

FPN No. 2: For systems that are not separately derived and 
are not required to be grounded as specified in 250.30, see 
445.13 for minimum size of conductors that must carry 
fault current. 

250.21 Alternating-Current Systems of 50 Volts to 1000 
Volts Not Required to Be Grounded. The following ac 
systems of 50 volts to 1000 volts shall be permitted to be 
grounded but shall not be required to be grounded: 

(1) Electric systems used exclusively to supply industrial 
electric furnaces for melting, refining, tempering, and 
the like 

(2) Separately derived systems used exclusively for recti- 
fiers that supply only adjustable-speed industrial drives 

(3) Separately derived systems supplied by transformers 
that have a primary voltage rating less than 1000 volts, 
provided that all the following conditions are met: 

a. The system is used exclusively for control circuits. 

b. The conditions of maintenance and supervision en- 
sure that only qualified persons service the installa- 
tion. 

c. Continuity of control power is required. 

d. Ground detectors are installed on the control sys- 
tem. 



(4) High-impedance grounded neutral systems as specified 
in 250.36 

(5) Other systems that are not required to be grounded in 
accordance with the requirements of 250.20(B) 

250.22 Circuits Not to Be Grounded. The following cir- 
cuits shall not be grounded: 

(1) Cranes (circuits for electric cranes operating over com- 
bustible fibers in Class III locations, as provided in 
503.13) 

(2) Health care facilities (circuits as provided in Article 
517) 

(3) Electrolytic cells (circuits as provided in Article 668) 

(4) Lighting systems [secondary circuits as provided in 
411.5(A)] 

250.24 Grounding Service-Supplied Alternating- 
Current Systems. 

(A) System Grounding Connections. A premises wiring 
system supplied by a grounded ac service shall have a 
grounding electrode conductor connected to the grounded 
service conductor, at each service, in accordance with 
250.24(A)(1) through (A)(5). 

(1) General. The connection shall be made at any acces- 
sible point from the load end of the service drop or service 
lateral to and including the terminal or bus to which the 
grounded service conductor is connected at the service dis- 
connecting means. 

FPN: See definitions of Service Drop and Service Lateral 
in Article 100. 

(2) Outdoor Transformer. Where the transformer supply- 
ing the service is located outside the building, at least one 
additional grounding connection shall be made from the 
grounded service conductor to a grounding electrode, either 
at the transformer or elsewhere outside the building. 

Exception: The additional grounding connection shall not 
be made on high-impedance grounded neutral systems. The 
system shall meet the requirements of 250.36. 

(3) Dual Fed Services. For services that are dual fed 
(double ended) in a common enclosure or grouped together 
in separate enclosures and employing a secondary tie, a 
single grounding electrode connection to the tie point of the 
grounded circuit conductors from each power source shall 
be permitted. 

(4) Main Bonding Jumper as Wire or Busbar. Where the 
main bonding jumper specified in 250.28 is a wire or bus- 
bar and is installed from the neutral bar or bus to the equip- 
ment grounding terminal bar or bus in the service equip- 
ment, the grounding electrode conductor shall be permitted 



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ARTICLE 250 — GROUNDING 



to be connected to the equipment grounding terminal bar or 
bus to which the main bonding jumper is connected. 

(5) Load-Side Grounding Connections. A grounding 
connection shall not be made to any grounded circuit con- 
ductor on the load side of the service disconnecting means 
except as otherwise permitted in this article. 

FPN: See 250.30(A) for separately derived systems, 
250.32 for connections at separate buildings or structures, 
and 250.142 for use of the grounded circuit conductor for 
grounding equipment. 

(B) Grounded Conductor Brought to Service Equipment. 

Where an ac system operating at less than 1000 volts is 
grounded at any point, the grounded conductor(s) shall be 
run to each service disconnecting means and shall be 
bonded to each disconnecting means enclosure. The 
grounded conductor(s) shall be installed in accordance with 
250.24(B)(1) through (B)(3). 

Exception: Where more than one service disconnecting 
means are located in an assembly listed for use as service 
equipment, it shall be permitted to run the grounded con- 
ductors) to the assembly, and the conductor(s) shall be 
bonded to the assembly enclosure. 

(1) Routing and Sizing. This conductor shall be routed 
with the phase conductors and shall not be smaller than the 
required grounding electrode conductor specified in Table 
250.66 but shall not be required to be larger than the largest 
ungrounded service-entrance phase conductor. In addition, 
for service-entrance phase conductors larger than 1100 kc- 
mil copper or 1750 kcmil aluminum, the grounded conduc- 
tor shall not be smaller than 12V2 percent of the area of the 
largest service-entrance phase conductor. The grounded ser- 
vice entrance conductor of a 3-phase, 3-wire delta service 
shall have an ampacity not less than the ungrounded con- 
ductors. 

(2) Parallel Conductors. Where the service-entrance 
phase conductors are installed in parallel, the size of the 
grounded conductor shall be based on the total circular mil 
area of the parallel conductors as indicated in this section. 
Where installed in two or more raceways, the size of the 
grounded conductor in each raceway shall be based on the 
size of the ungrounded service-entrance conductor in the 
raceway but not smaller than 1/0 AWG. 

FPN: See 310.4 for grounded conductors connected in 
parallel. 

(3) High Impedance. The grounded conductor on a high- 
impedance grounded neutral system shall be grounded in 
accordance with 250.36. 

(C) Grounding Electrode Conductor. A grounding elec- 
trode conductor shall be used to connect the equipment 



grounding conductors, the service-equipment enclosures, 
and, where the system is grounded, the grounded service 
conductor to the grounding electrode(s) required by Part III 
of this article. 

High-impedance grounded neutral system connections 
shall be made as covered in 250.36. 

FPN: See 250.24(A) for ac system grounding connections. 

(D) Ungrounded System Grounding Connections. A 

premises wiring system that is supplied by an ac service 
that is ungrounded shall have, at each service, a grounding 
electrode conductor connected to the grounding elec- 
trode^) required by Part III of this article. The grounding 
electrode conductor shall be connected to a metal enclosure 
of the service conductors at any accessible point from the 
load end of the service drop or service lateral to the service 
disconnecting means. 

250.26 Conductor to Be Grounded — Alternating- 
Current Systems. For ac premises wiring systems, the 
conductor to be grounded shall be as specified in the fol- 
lowing: 

(1) Single-phase, 2-wire — one conductor 

(2) Single-phase, 3-wire — the neutral conductor 

(3) Multiphase systems having one wire common to all 
phases — the common conductor 

(4) Multiphase systems where one phase is grounded — 
one phase conductor 

(5) Multiphase systems in which one phase is used as 
in (2) — the neutral conductor 

250.28 Main Bonding Jumper. For a grounded system, an 
unspliced main bonding jumper shall be used to connect the 
equipment grounding conductor(s) and the service- 
disconnect enclosure to the grounded conductor of the sys- 
tem within the enclosure for each service disconnect. 

Exception No. 1: Where more than one service disconnect- 
ing means is located in an assembly listed for use as ser- 
vice equipment, an unspliced main bonding jumper shall 
bond the grounded conductor(s) to the assembly enclosure. 
Exception No. 2: Impedance grounded neutral systems 
shall be permitted to be connected as provided in 250.36 
and 250.186. 

(A) Material. Main bonding jumpers shall be of copper or 
other corrosion-resistant material. A main bonding jumper 
shall be a wire, bus, screw, or similar suitable conductor. 

(B) Construction. Where a main bonding jumper is a 
screw only, the screw shall be identified with a green finish 
that shall be visible with the screw installed. 

(C) Attachment. Main bonding jumpers shall be attached 
in the manner specified by the applicable provisions of 
250.8. 



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ARTICLE 250 — GROUNDING 



70-101 



(D) Size. The main bonding jumper shall not be smaller 
than the sizes shown in Table 250.66 for grounding elec- 
trode conductors. Where the service-entrance phase con- 
ductors are larger than 1100 kcmil copper or 1750 kcmil 
aluminum, the bonding jumper shall have an area that is not 
less than 12V2 percent of the area of the largest phase con- 
ductor except that, where the phase conductors and the 
bonding jumper are of different materials (copper or alumi- 
num), the minimum size of the bonding jumper shall be 
based on the assumed use of phase conductors of the same 
material as the bonding jumper and with an ampacity 
equivalent to that of the installed phase conductors. 

250.30 Grounding Separately Derived Alternating- 
Current Systems. 

(A) Grounded Systems. A separately derived ac system 
that is grounded shall comply with 250.30(A)(1) through 
(6). 

Exception: High-impedance grounded neutral system 
grounding connection requirements shall not be required to 
comply with 250.30(A)(1) and (2) and shall be made as 
specified in 250.36 and 250.186. 

(1) Bonding Jumper. A bonding jumper in compliance 
with 250.28(A) through (D) that is sized for the derived 
phase conductors shall be used to connect the equipment 
grounding conductors of the separately derived system to 
the grounded conductor. Except as permitted by 
250.24(A)(3), this connection shall be made at any point on 
the separately derived system from the source to the first 
system disconnecting means or overcurrent device, or it 
shall be made at the source of a separately derived system 
that has no disconnecting means or overcurrent devices. 
The point of connection shall be the same as the grounding 
electrode conductor as required in 250.30(A)(2). 

Exception No. 1: A bonding jumper at both the source and 
the first disconnecting means shall be permitted where do- 
ing so does not establish a parallel path for the grounded 
circuit conductor. Where a grounded conductor is used in 
this manner, it shall not be smaller than the size specified, 
for the bonding jumper but shall not be required to be 
larger than the ungrounded conductor(s). For the purposes 
of this exception, connection through the earth shall not be 
considered as providing a parallel path. 

Exception No. 2: The size of the bonding jumper for a 
system that supplies a Class 1, Class 2, or Class 3 circuit, 
and is derived from a transformer rated not more than 1000 
volt-amperes, shall not be smaller than the derived phase 
conductors and shall not be smaller than 14 AWG copper 
or 12 AWG aluminum. 

(2) Grounding Electrode Conductor. The grounding 
electrode conductor shall be installed in accordance with 



(a) or (b). Where taps are connected to a common ground- 
ing electrode conductor, the installation shall comply with 
250.30(A)(3). 

(a) Single Separately Derived System. A grounding 
electrode conductor for a single separately derived system 
shall be sized in accordance with 250.66 for the derived 
phase conductors and shall be used to connect the grounded 
conductor of the derived system to the grounding electrode 
as specified in 250.30(A)(4). Except as permitted by 
250.24(A)(3) or (A)(4), this connection shall be made at the 
same point on the separately derived system where the 
bonding jumper is installed. 

Exception: A grounding electrode conductor shall not be 
required for a system that supplies a Class 1, Class 2, or 
Class 3 circuit and is derived from a transformer rated not 
more than 1000 volt-amperes, provided the system 
grounded conductor is bonded to the transformer frame or 
enclosure by a jumper sized in accordance with 
250.30(A)(1), Exception No. 2, and the transformer frame 
or enclosure is grounded by one of the means specified in 
250.134. 

(b) Multiple Separately Derived Systems. Where more 
than one separately derived system is connected to a com- 
mon grounding electrode conductor as provided in 
250.30(A)(3), the common grounding electrode conductor 
shall be sized in accordance with 250.66, based on the total 
area of the largest derived phase conductor from each sepa- 
rately derived system. 

(3) Grounding Electrode Conductor Taps. It shall be 
permissible to connect taps from a separately derived sys- 
tem to a common grounding electrode conductor. Each tap 
conductor shall connect the grounded conductor of the 
separately derived system to the common grounding elec- 
trode conductor. 

(a) Tap Conductor Size. Each tap conductor shall be 
sized in accordance with 250.66 for the derived phase con- 
ductors of the separately derived system it serves. 

(b) Connections. All connections shall be made at an 
accessible location by an irreversible compression connec- 
tor listed for the purpose, listed connections to copper bus- 
bars not less than 6 mm x 50 mm ( ] A in. x 2 in.), or by the 
exothermic welding process. The tap conductors shall be 
connected to the common grounding electrode conductor as 
specified in 250.30(A)(2)(b) in such a manner that the com- 
mon grounding electrode conductor remains without a 
splice or joint. 

(c) Installation. The common grounding electrode con- 
ductor and the taps to each separately derived system shall 
comply with 250.64(A), (B), (C), and (E). 

(d) Bonding. Where exposed structural steel that is 
interconnected to form the building frame or interior metal 
piping exists in the area served by the separately derived 



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ARTICLE 250 — GROUNDED 



system, it shall be bonded to the grounding electrode con- 
ductor in accordance with 250.104. 

(4) Grounding Electrode. The grounding electrode shall 
be as near as practicable to and preferably in the same area 
as the grounding electrode conductor connection to the sys- 
tem. The grounding electrode shall be the nearest one of the 
following: 

(1) An effectively grounded structural metal member of the 
structure 

(2) An effectively grounded metal water pipe within 1.5 m 
(5 ft) from the point of entrance into the building 

Exception: In industrial and commercial buildings where 
conditions of maintenance and supervision ensure that only 
qualified persons service the installation and the entire 
length of the interior metal water pipe that is being used for 
the grounding electrode is exposed, the connection shall be 
permitted at any point on the water pipe system. 

(3) Other electrodes as specified by 250.52 where the elec- 
trodes specified by 250.30(A)(4)(1) or (A)(4)(2) are not 
available 

Exception to (I), (2), and (3): Where a separately derived 
system originates in listed equipment suitable for use as 
service equipment, the grounding electrode used for the 
service or feeder shall be permitted as the grounding elec- 
trode for the separately derived system, provided the 
grounding electrode conductor from the service or feeder to 
the grounding electrode is of sufficient size for the sepa- 
rately derived system. Where the equipment ground bus 
internal to the service equipment is not smaller than the 
required grounding electrode conductor, the grounding 
electrode connection for the separately derived system shall 
be permitted to be made to the bus. 

FPN: See 250.104(A)(4) for bonding requirements of inte- 
rior metal water piping in the area served by separately 
derived systems. 

(5) Equipment Bonding Jumper Size. Where a bonding 
jumper is run with the derived phase conductors from the 
source of a separately derived system to the first discon- 
necting means, it shall be sized in accordance with 
250.28(A) through (D), based on the size of the derived 
phase conductors. 

(6) Grounded Conductor. Where a grounded conductor is 
installed and the bonding jumper is not located at the 
source of the separately derived system, the following shall 
apply: 

(a) Routing and Sizing. This conductor shall be routed 
with the derived phase conductors and shall not be smaller 
than the required grounding electrode conductor specified 
in Table 250.66, but shall not be required to be larger than 
the largest ungrounded derived phase conductor. In addi- 



tion, for phase conductors larger than 1100 kcmil copper or 
1750 kcmil aluminum, the grounded conductor shall not be 
smaller than YlVi percent of the area of the largest derived 
phase conductor. The grounded conductor of a 3-phase, 
3-wire delta system shall have an ampacity not less than the 
ungrounded conductors. 

(b) Parallel Conductors. Where the derived phase con- 
ductors are installed in parallel, the size of the grounded 
conductor shall be based on the total circular mil area of the 
parallel conductors as indicated in this section. Where in- 
stalled in two or more raceways, the size of the grounded 
conductor in each raceway shall be based on the size of the 
ungrounded conductors in the raceway but not smaller than 
1/0 AWG. 

FPN: See 310.4 for grounded conductors connected in 
parallel. 

(c) High Impedance. The grounded conductor on a 
high-impedance grounded neutral system shall be grounded 
in accordance with 250.36. 

(B) Ungrounded Systems. The equipment of an un- 
grounded separately derived system shall be grounded as 
specified in 250.30(B)(1) and (2). 

(1) Grounding Electrode Conductor. A grounding elec- 
trode conductor, sized in accordance with 250.66 for the 
derived phase conductors, shall be used to connect the 
metal enclosures of the derived system to the grounding 
electrode as specified in 250.30(B)(2). This connection 
shall be made at any point on the separately derived system 
from the source to the first system disconnecting means. 

(2) Grounding Electrode. Except as permitted by 250.34 
for portable and vehicle-mounted generators, the grounding 
electrode shall comply with 250.30(A)(4). 

250.32 Two or More Buildings or Structures Supplied 
from a Common Service. 

(A) Grounding Electrode. Where two or more buildings 
or structures are supplied from a common ac service by a 
feeder(s) or branch circuit(s), the grounding electrode(s) 
required in Part III of this article at each building or struc- 
ture shall be connected in the manner specified in 
250.32(B) or (C). Where there are no existing grounding 
electrodes, the grounding electrode(s) required in Part III of 
this article shall be installed. 

Exception: A grounding electrode at separate buildings or 
structures shall not be required where only one branch 
circuit supplies the building or structure and the branch 
circuit includes an equipment grounding conductor for 
grounding the conductive non-current-carrying parts of all 
equipment. 



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ARTICLE 250 — GROUNDING 



70-103 



(B) Grounded Systems. For a grounded system at the 
separate building or structure, the connection to the ground- 
ing electrode and grounding or bonding of equipment, 
structures, or frames required to be grounded or bonded 
shall comply with either 250.32(B)(1) or (2). 

(1) Equipment Grounding Conductor. An equipment 
grounding conductor as described in 250.118 shall be run 
with the supply conductors and connected to the building or 
structure disconnecting means and to the grounding elec- 
trode^). The equipment grounding conductor shall be used 
for grounding or bonding of equipment, structures, or 
frames required to be grounded or bonded. The equipment 
grounding conductor shall be sized in accordance with 
250.122. Any installed grounded conductor shall not be 
connected to the equipment grounding conductor or to the 
grounding electrode(s). 

(2) Grounded Conductor. Where (1) an equipment 
grounding conductor is not run with the supply to the build- 
ing or structure, (2) there are no continuous metallic paths 
bonded to the grounding system in both buildings or struc- 
tures involved, and (3) ground-fault protection of equip- 
ment has not been installed on the common ac service, the 
grounded circuit conductor run with the supply to the build- 
ing or structure shall be connected to the building or struc- 
ture disconnecting means and to the grounding electrode(s) 
and shall be used for grounding or bonding of equipment, 
structures, or frames required to be grounded or bonded. 
The size of the grounded conductor shall not be smaller 
than the larger of 

(1) That required by 220.22 

(2) That required by 250.122 

(C) Ungrounded Systems. The grounding electrode(s) 
shall be connected to the building or structure disconnect- 
ing means. 

(D) Disconnecting Means Located in Separate Building 
or Structure on the Same Premises. Where one or more 
disconnecting means supply one or more additional build- 
ings or structures under single management, and where 
these disconnecting means are located remote from those 
buildings or structures in accordance with the provisions of 
225.32, Exception Nos. 1 and 2, all of the following con- 
ditions shall be met: 

(1) The connection of the grounded circuit conductor to the 
grounding electrode at a separate building or structure 
shall not be made. 

(2) An equipment grounding conductor for grounding any 
non-current-carrying equipment, interior metal piping 
systems, and building or structural metal frames is run 
with the circuit conductors to a separate building or 
structure and bonded to existing grounding electrode(s) 



required in Part III of this article, or, where there are no 
existing electrodes, the grounding electrode(s) required 
in Part III of this article shall be installed where a 
separate building or structure is supplied by more than 
one branch circuit. 
(3) Bonding the equipment grounding conductor to the 
grounding electrode at a separate building or structure 
shall be made in a junction box, panelboard, or similar 
enclosure located immediately inside or outside the 
separate building or structure. 

(E) Grounding Electrode Conductor. The size of the 
grounding electrode conductor to the grounding elec- 
trode^) shall not be smaller than given in 250.66, based on 
the largest ungrounded supply conductor. The installation 
shall comply with Part III of this article. 

250.34 Portable and Vehicle-Mounted Generators. 

(A) Portable Generators. The frame of a portable genera- 
tor shall not be required to be grounded and shall be per- 
mitted to serve as the grounding electrode for a system 
supplied by the generator under the following conditions: 

(1) The generator supplies only equipment mounted on the 
generator, cord-and-plug-connected equipment through 
receptacles mounted on the generator, or both, and 

(2) The non-current-carrying metal parts of equipment and 
the equipment grounding conductor terminals of the 
receptacles are bonded to the generator frame. 

(B) Vehicle-Mounted Generators. The frame of a vehicle 
shall be permitted to serve as the grounding electrode for a 
system supplied by a generator located on the vehicle under 
the following conditions: 

(1) The frame of the generator is bonded to the vehicle 
frame, and 

(2) The generator supplies only equipment located on the 
vehicle or cord-and-plug-connected equipment through 
receptacles mounted on the vehicle, or both equipment 
located on the vehicle and cord-and-plug-connected 
equipment through receptacles mounted on the vehicle 
or on the generator, and 

(3) The non-current-carrying metal parts of equipment and 
the equipment grounding conductor terminals of the 
receptacles are bonded to the generator frame, and 

(4) The system complies with all other provisions of this 
article. 

(C) Grounded Conductor Bonding. A system conductor 
that is required to be grounded by 250.26 shall be bonded 
to the generator frame where the generator is a component 
of a separately derived system. 

FPN: For grounding portable generators supplying fixed 
wiring systems, see 250.20(D). 



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ARTICLE 250 — GROUNDING 



250.36 High-Impedance Grounded Neutral Systems. 

High-impedance grounded neutral systems in which a 
grounding impedance, usually a resistor, limits the ground- 
fault current to a low value shall be permitted for 3 -phase 
ac systems of 480 volts to 1000 volts where all the follow- 
ing conditions are met: 

(1) The conditions of maintenance and supervision ensure 
that only qualified persons service the installation. 

(2) Continuity of power is required. 

(3) Ground detectors are installed on the system. 

(4) Line-to-neutral loads are not served. 

High-impedance grounded neutral systems shall com- 
ply with the provisions of 250.36(A) through (G). 

(A) Grounding Impedance Location. The grounding im- 
pedance shall be installed between the grounding electrode 
conductor and the system neutral. Where a neutral is not 
available, the grounding impedance shall be installed be- 
tween the grounding electrode conductor and the neutral 
derived from a grounding transformer. 

(B) Neutral Conductor. The neutral conductor from the 
neutral point of the transformer or generator to its connec- 
tion point to the grounding impedance shall be fully insu- 
lated. 

The neutral conductor shall have an ampacity of not 
less than the maximum current rating of the grounding im- 
pedance. In no case shall the neutral conductor be smaller 
than 8 AWG copper or 6 AWG aluminum or copper-clad 
aluminum. 

(C) System Neutral Connection. The system neutral con- 
ductor shall not be connected to ground except through the 
grounding impedance. 

FPN: The impedance is normally selected to limit the 
ground-fault current to a value slightly greater than or equal 
to the capacitive charging current of the system. This value 
of impedance will also limit transient overvoltages to safe 
values. For guidance, refer to criteria for limiting transient 
overvoltages in ANSI/IEEE 142-1991, Recommended 
Practice for Grounding of Industrial and Commercial 
Power Systems. 

(D) Neutral Conductor Routing. The conductor connect- 
ing the neutral point of the transformer or generator to the 
grounding impedance shall be permitted to be installed in a 
separate raceway. It shall not be required to run this con- 
ductor with the phase conductors to the first system discon- 
necting means or overcurrent device. 

(E) Equipment Bonding Jumper. The equipment bond- 
ing jumper (the connection between the equipment ground- 
ing conductors and the grounding impedance) shall be an 
unspliced conductor run from the first system disconnecting 
means or overcurrent device to the grounded side of the 
grounding impedance. 



(F) Grounding Electrode Conductor Location. The 

grounding electrode conductor shall be attached at any 
point from the grounded side of the grounding impedance 
to the equipment grounding connection at the service 
equipment or first system disconnecting means. 

(G) Equipment Bonding Jumper Size. The equipment 
bonding jumper shall be sized in accordance with (1) or (2). 

(1) Where the grounding electrode conductor connection is 
made at the grounding impedance, the equipment bond- 
ing jumper shall be sized in accordance with 250.66, 
based on the size of the service entrance conductors for 
a service or the derived phase conductors for a sepa- 
rately derived system. 

(2) Where the grounding electrode conductor is connected 
at the first system disconnecting means or overcurrent 
device, the equipment bonding jumper shall be sized 
the same as the neutral conductor in 250.36(B). 

III. Grounding Electrode System and Grounding 
Electrode Conductor 

250.50 Grounding Electrode System. If available on the 
premises at each building or structure served, each item in 
250.52(A)(1) through (A)(6) shall be bonded together to 
form the grounding electrode system. Where none of these 
electrodes are available, one or more of the electrodes 
specified in 250.52(A)(4) through (A)(7) shall be installed 
and used. 

250.52 Grounding Electrodes. 

(A) Electrodes Permitted for Grounding. 

(1) Metal Underground Water Pipe. A metal under- 
ground water pipe in direct contact with the earth for 3.0 m 
(10 ft) or more (including any metal well casing effectively 
bonded to the pipe) and electrically continuous (or made 
electrically continuous by bonding around insulating joints 
or insulating pipe) to the points of connection of the 
grounding electrode conductor and the bonding conductors. 
Interior metal water piping located more than 1.52 m (5 ft) 
from the point of entrance to the building shall not be used 
as a part of the grounding electrode system or as a conduc- 
tor to interconnect electrodes that are part of the grounding 
electrode system. 

Exception: In industrial and commercial buildings or 
structures where conditions of maintenance and supervi- 
sion ensure that only qualified persons service the installa- 
tion, interior metal water piping located more than 1.52 m 
(5 ft) from the point of entrance to the building shall be 
permitted as a part of the grounding electrode system or as 
a conductor to interconnect electrodes that are part of the 
grounding electrode system, provided that the entire length, 



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ARTICLE 250 — GROUNDING 



70-105 



other than short sections passing perpendicular through 
walls, floors, or ceilings, of the interior metal water pipe 
that is being used for the conductor is exposed. 

(2) Metal Frame of the Building or Structure. The metal 
frame of the building or structure, where effectively 
grounded. 

(3) Concrete-Encased Electrode. An electrode encased 
by at least 50 mm (2 in.) of concrete, located within and 
near the bottom of a concrete foundation or footing that is 
in direct contact with the earth, consisting of at least 6.0 m 
(20 ft) of one or more bare or zinc galvanized or other 
electrically conductive coated steel reinforcing bars or rods 
of not less than 13 mm (¥2 in.) in diameter, or consisting of 
at least 6.0 m (20 ft) of bare copper conductor not smaller 
than 4 AWG. Reinforcing bars shall be permitted to be 
bonded together by the usual steel tie wires or other effec- 
tive means. 

(4) Ground Ring. A ground ring encircling the building or 
structure, in direct contact with the earth, consisting of at 
least 6.0 m (20 ft) of bare copper conductor not smaller 
than 2 AWG. 

(5) Rod and Pipe Electrodes. Rod and pipe electrodes 
shall not be less than 2.5 m (8 ft) in length and shall consist 
of the following materials. 

(a) Electrodes of pipe or conduit shall not be smaller 
than metric designator 21 (trade size 3 A) and, where of iron 
or steel, shall have the outer surface galvanized or other- 
wise metal-coated for corrosion protection. 

(b) Electrodes of rods of iron or steel shall be at least 
15.87 mm ( 5 /s in.) in diameter. Stainless steel rods less than 
16 mm (% in.) in diameter, nonferrous rods, or their 
equivalent shall be listed and shall not be less than 13 mm 
(V2 in.) in diameter. 

(6) Plate Electrodes. Each plate electrode shall expose not 
less than 0.186 m 2 (2 ft 2 ) of surface to exterior soil. Elec- 
trodes of iron or steel plates shall be at least 6.4 mm (}A in.) 
in thickness. Electrodes of nonferrous metal shall be at least 
1.5 mm (0.06 in.) in thickness. 

(7) Other Local Metal Underground Systems or 
Structures. Other local metal underground systems or 
structures such as piping systems and underground tanks. 

(B) Electrodes Not Permitted for Grounding. The fol- 
lowing shall not be used as grounding electrodes: 

(1) Metal underground gas piping system 

(2) Aluminum electrodes 

250.53 Grounding Electrode System Installation. 

FPN: See 547.9 and 547.10 for special grounding and 
bonding requirements for agricultural buildings. 



(A) Rod, Pipe, and Plate Electrodes. Where practicable, 
rod, pipe, and plate electrodes shall be embedded below 
permanent moisture level. Rod, pipe, and plate electrodes 
shall be free from nonconductive coatings such as paint or 
enamel. 

(B) Electrode Spacing. Where more than one of the elec- 
trodes of the type specified in 250.52(A)(5) or (A)(6) are 
used, each electrode of one grounding system (including 
that used for air terminals) shall not be less than 1.83 m 
(6 ft) from any other electrode of another grounding sys- 
tem. Two or more grounding electrodes that are effectively 
bonded together shall be considered a single grounding 
electrode system. 

(C) Bonding Jumper. The bonding jumper(s) used to con- 
nect the grounding electrodes together to form the ground- 
ing electrode system shall be installed in accordance with 
250.64(A), (B), and (E), shall be sized in accordance with 
250.66, and shall be connected in the manner specified in 
250.70. 

(D) Metal Underground Water Pipe. Where used as a 
grounding electrode, metal underground water pipe shall 
meet the requirements of 250.53(D)(1) and (D)(2). 

(1) Continuity. Continuity of the grounding path or the 
bonding connection to interior piping shall not rely on wa- 
ter meters or filtering devices and similar equipment. 

(2) Supplemental Electrode Required. A metal under- 
ground water pipe shall be supplemented by an additional 
electrode of a type specified in 250.52(A)(2) through 
(A)(7). Where the supplemental electrode is a rod, pipe, or 
plate type, it shall comply with 250.56. The supplemental 
electrode shall be permitted to be bonded to the grounding 
electrode conductor, the grounded service-entrance conduc- 
tor, the nonflexible grounded service raceway, or any 
grounded service enclosure. 

Exception: The supplemental electrode shall be permitted 
to be bonded to the interior metal water piping at any 
convenient point as covered in 250.52(A)(1), Exception. 

(E) Supplemental Electrode Bonding Connection Size. 

Where the supplemental electrode is a rod, pipe, or plate 
electrode, that portion of the bonding jumper that is the sole 
connection to the supplemental grounding electrode shall 
not be required to be larger than 6 AWG copper wire or 4 
AWG aluminum wire. 

(F) Ground Ring. The ground ring shall be buried at a 
depth below the earth's surface of not less than 750 mm 
(30 in.). 



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70-106 



ARTICLE 250 — GROUNDING 



(G) Rod and Pipe Electrodes. The electrode shall be in- 
stalled such that at least 2.44 m (8 ft) of length is in contact 
with the soil. It shall be driven to a depth of not less than 
2.44 m (8 ft) except that, where rock bottom is encoun- 
tered, the electrode shall be driven at an oblique angle not 
to exceed 45 degrees from the vertical or, where rock bot- 
tom is encountered at an angle up to 45 degrees, the elec- 
trode shall be permitted to be buried in a trench that is at 
least 750 mm (30 in.) deep. The upper end of the electrode 
shall be flush with or below ground level unless the above- 
ground end and the grounding electrode conductor attach- 
ment are protected against physical damage as specified in 
250.10. 

(H) Plate Electrode. Plate electrodes shall be installed not 
less than 750 mm (30 in.) below the surface of the earth. 

250.54 Supplementary Grounding Electrodes. 

Supplementary grounding electrodes shall be permitted to 
be connected to the equipment grounding conductors speci- 
fied in 250.118 and shall not be required to comply with the 
electrode bonding requirements of 250.50 or 250.53(C) or 
the resistance requirements of 250.56, but the earth shall 
not be used as the sole equipment grounding conductor. 

250.56 Resistance of Rod, Pipe, and Plate Electrodes. A 

single electrode consisting of a rod, pipe, or plate that does 
not have a resistance to ground of 25 ohms or less shall be 
augmented by one additional electrode of any of the types 
specified by 250.52(A)(2) through (A)(7). Where multiple 
rod, pipe, or plate electrodes are installed to meet the re- 
quirements of this section, they shall not be less than 1.8 m 
(6 ft) apart. 

FPN: The paralleling efficiency of rods longer than 2.5 m 
(8 ft) is improved by spacing greater than 1.8 m (6 ft). 

250.58 Common Grounding Electrode. Where an ac sys- 
tem is connected to a grounding electrode in or at a build- 
ing as specified in 250.24 and 250.32, the same electrode 
shall be used to ground conductor enclosures and equip- 
ment in or on that building. Where separate services supply 
a building and are required to be connected to a grounding 
electrode, the same grounding electrode shall be used. 

Two or more grounding electrodes that are effectively 
bonded together shall be considered as a single grounding 
electrode system in this sense. 

250.60 Use of Air Terminals. Air terminal conductors and 
driven pipes, rods, or plate electrodes used for grounding 
air terminals shall not be used in lieu of the grounding 
electrodes required by 250.50 for grounding wiring systems 
and equipment. This provision shall not prohibit the re- 
quired bonding together of grounding electrodes of differ- 
ent systems. 



FPN No. 1: See 250.106 for spacing from air terminals. 
See 800.40(D), 810.21 (J), and 820.40(D) for bonding of 
electrodes. 

FPN No. 2: Bonding together of all separate grounding 
electrodes will limit potential differences between them and 
between their associated wiring systems. 

250.62 Grounding Electrode Conductor Material. The 

grounding electrode conductor shall be of copper, alumi- 
num, or copper-clad aluminum. The material selected shall 
be resistant to any corrosive condition existing at the instal- 
lation or shall be suitably protected against corrosion. The 
conductor shall be solid or stranded, insulated, covered, or 
bare. 

250.64 Grounding Electrode Conductor Installation. 

Grounding electrode conductors shall be installed as speci- 
fied in 250.64(A) through (F). 

(A) Aluminum or Copper-Clad Aluminum Conductors. 

Bare aluminum or copper-clad aluminum grounding con- 
ductors shall not be used where in direct contact with ma- 
sonry or the earth or where subject to corrosive conditions. 
Where used outside, aluminum or copper-clad aluminum 
grounding conductors shall not be terminated within 
450 mm (18 in.) of the earth. 

(B) Securing and Protection from Physical Damage. A 

grounding electrode conductor or its enclosure shall be se- 
curely fastened to the surface on which it is carried. A 4 
AWG copper or aluminum or larger conductor shall be 
protected if exposed to severe physical damage. A 6 AWG 
grounding conductor that is free from exposure to physical 
damage shall be permitted to be run along the surface of the 
building construction without metal covering or protection 
where it is securely fastened to the construction; otherwise, 
it shall be in rigid metal conduit, intermediate metal con- 
duit, rigid nonmetallic conduit, electrical metallic tubing, or 
cable armor. Grounding conductors smaller than 6 AWG 
shall be in rigid metal conduit, intermediate metal conduit, 
rigid nonmetallic conduit, electrical metallic tubing, or 
cable armor. 

(C) Continuous. The grounding electrode conductor shall 
be installed in one continuous length without a splice or 
joint, unless spliced only by irreversible compression-type 
connectors listed for the purpose or by the exothermic 
welding process. 

Exception: Sections of busbars shall be permitted to be 
connected together to form a grounding electrode 
conductor. 

(D) Grounding Electrode Conductor Taps. Where a ser- 
vice consists of more than a single enclosure as permitted 
in 230.40, Exception No. 2, it shall be permitted to connect 



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ARTICLE 250 — GROUNDING 



70-107 



taps to the grounding electrode conductor. Each such tap 
conductor shall extend to the inside of each such enclosure. 
The grounding electrode conductor shall be sized in accor- 
dance with 250.66, but the tap conductors shall be permit- 
ted to be sized in accordance with the grounding electrode 
conductors specified in 250.66 for the largest conductor 
serving the respective enclosures. The tap conductors shall 
be connected to the grounding electrode conductor in such 
a manner that the grounding electrode conductor remains 
without a splice. 

(E) Enclosures for Grounding Electrode Conductors. 

Metal enclosures for grounding electrode conductors shall 
be electrically continuous from the point of attachment to 
cabinets or equipment to the grounding electrode and shall 
be securely fastened to the ground clamp or fitting. Metal 
enclosures that are not physically continuous from cabinet 
or equipment to the grounding electrode shall be made 
electrically continuous by bonding each end to the ground- 
ing electrode conductor. Where a raceway is used as pro- 
tection for a grounding electrode conductor, the installation 
shall comply with the requirements of the appropriate race- 
way article. 

(F) To Electrode(s). A grounding electrode conductor 
shall be permitted to be run to any convenient grounding 
electrode available in the grounding electrode system or to 
one or more grounding electrode(s) individually. The 
grounding electrode conductor shall be sized for the largest 
grounding electrode conductor required among all the elec- 
trodes connected to it. 



Table 250.66 Grounding Electrode Conductor for 
Alternating-Current Systems 



Size of Largest Ungrounded 
Service-Entrance Conductor 






or Equivalent Area for 
Parallel Conductors 3 


Size of Grounding 
Electrode Conductor 


(AWG/kcmil) 


(AWG/kcmil) 




Aluminum or 




Aluminum or 


Copper 


Copper-Clad 
Aluminum 


Copper 


Copper-Clad 
Aluminum 13 


2 or smaller 


1/0 or smaller 


8 


6 


1 or 1/0 


2/0 or 3/0 


6 


4 


2/0 or 3/0 


4/0 or 250 


4 


2 


Over 3/0 


Over 250 


2 


1/0 


through 350 
Over 350 


through 500 
Over 500 


1/0 


3/0 


through 600 
Over 600 


through 900 
Over 900 


2/0 


4/0 


through 
1100 


through 
1750 






Over 1100 


Over 1750 


3/0 


250 



Notes: 

1. Where multiple sets of service-entrance conductors are used as 
permitted in 230.40, Exception No. 2, the equivalent size of the larg- 
est service-entrance conductor shall be determined by the largest sum 
of the areas of the corresponding conductors of each set. 

2. Where there are no service-entrance conductors, the grounding 
electrode conductor size shall be determined by the equivalent size of 
the largest service-entrance conductor required for the load to be 
served. 

a This table also applies to the derived conductors of separately de- 
rived ac systems. 
b See installation restrictions in 250.64(A). 



250.66 Size of Alternating-Current Grounding Elec- 
trode Conductor. The size of the grounding electrode con- 
ductor of a grounded or ungrounded ac system shall not be 
less than given in Table 250.66, except as permitted in 
250.66(A) through (C). 

FPN: See 250.24(B) for size of ac system conductor 
brought to service equipment. 

(A) Connections to Rod, Pipe, or Plate Electrodes. 

Where the grounding electrode conductor is connected to 
rod, pipe, or plate electrodes as permitted in 250.52(A)(5) 
or 250.52(A)(6), that portion of the conductor that is the 
sole connection to the grounding electrode shall not be 
required to be larger than 6 AWG copper wire or 4 AWG 
aluminum wire. 

(B) Connections to Concrete-Encased Electrodes. 

Where the grounding electrode conductor is connected to a 
concrete-encased electrode as permitted in 250.52(A)(3), 
that portion of the conductor that is the sole connection to 
the grounding electrode shall not be required to be larger 
than 4 AWG copper wire. 



(C) Connections to Ground Rings. Where the grounding 
electrode conductor is connected to a ground ring as per- 
mitted in 250.52(A)(4), that portion of the conductor that is 
the sole connection to the grounding electrode shall not be 
required to be larger than the conductor used for the ground 
ring. 

250.68 Grounding Electrode Conductor and Bonding 
Jumper Connection to Grounding Electrodes. 

(A) Accessibility. The connection of a grounding electrode 
conductor or bonding jumper to a grounding electrode shall 
be accessible. 

Exception: An encased or buried connection to a concrete- 
encased, driven, or buried grounding electrode shall not be 
required to be accessible. 

(B) Effective Grounding Path. The connection of a 
grounding electrode conductor or bonding jumper to a 
grounding electrode shall be made in a manner that will 
ensure a permanent and effective grounding path. Where 
necessary to ensure the grounding path for a metal piping 



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70-108 



ARTICLE 250 — GROUNDING 



system used as a grounding electrode, effective bonding 
shall be provided around insulated joints and around any 
equipment likely to be disconnected for repairs or replace- 
ment. Bonding conductors shall be of sufficient length to 
permit removal of such equipment while retaining the in- 
tegrity of the bond. 

250.70 Methods of Grounding and Bonding Conductor 
Connection to Electrodes. The grounding or bonding con- 
ductor shall be connected to the grounding electrode by 
exothermic welding, listed lugs, listed pressure connectors, 
listed clamps, or other listed means. Connections depend- 
ing on solder shall not be used. Ground clamps shall be 
listed for the materials of the grounding electrode and the 
grounding electrode conductor and, where used on pipe, 
rod, or other buried electrodes, shall also be listed for direct 
soil burial or concrete encasement. Not more than one con- 
ductor shall be connected to the grounding electrode by a 
single clamp or fitting unless the clamp or fitting is listed 
for multiple conductors. One of the following methods 
shall be used: 

(1) A pipe fitting, pipe plug, or other approved device 
screwed into a pipe or pipe fitting 

(2) A listed bolted clamp of cast bronze or brass, or plain 
or malleable iron 

(3) For indoor telecommunications purposes only, a listed 
sheet metal strap-type ground clamp having a rigid 
metal base that seats on the electrode and having a 
strap of such material and dimensions that it is not 
likely to stretch during or after installation 

(4) An equally substantial approved means 

IV. Enclosure, Raceway, and Service Cable Grounding 

250.80 Service Raceways and Enclosures. Metal enclo- 
sures and raceways for service conductors and equipment 
shall be grounded. 

Exception: A metal elbow that is installed in an under- 
ground installation of rigid nonmetallic conduit and is iso- 
lated from possible contact by a minimum cover of 450 mm 
(18 in.) to any part of the elbow shall not be required to be 
grounded. 

250.84 Underground Service Cable or Conduit. 

(A) Underground Service Cable. The sheath or armor of 
a continuous underground metal- sheathed service cable 
system that is metallically connected to the underground 
system shall not be required to be grounded at the building. 
The sheath or armor shall be permitted to be insulated from 
the interior conduit or piping. 

(B) Underground Service Conduit Containing Cable. 

An underground service conduit that contains a metal- 



sheathed cable bonded to the underground system shall not 
be required to be grounded at the building. The sheath or 
armor shall be permitted to be insulated from the interior 
conduit or piping. 

250.86 Other Conductor Enclosures and Raceways. 

Except as permitted by 250.112(1), metal enclosures and 
raceways for other than service conductors shall be 
grounded. 

Exception No. 1: Metal enclosures and raceways for con- 
ductors added to existing installations of open wire, knob 
and tube wiring, and nonmetallic- sheathed cable shall not 
be required to be grounded where these enclosures or wir- 
ing methods 

(a) Do not provide an equipment ground; 

(b) Are in runs of less than 7.5 m (25 ft); 

(c) Are free from probable contact with ground, grounded 
metal, metal lath, or other conductive material; and 

(d) Are guarded against contact by persons. 

Exception No. 2: Short sections of metal enclosures or 
raceways used to provide support or protection of cable 
assemblies from physical damage shall not be required to 
be grounded. 

Exception No. 3: A metal elbow shall not be required to be 
grounded where it is installed in a nonmetallic raceway 
and is isolated from possible contact by a minimum cover 
of 450 mm (18 in.) to any part of the elbow or is encased in 
not less than 50 mm (2 in.) of concrete. 

V. Bonding 

250.90 General. Bonding shall be provided where neces- 
sary to ensure electrical continuity and the capacity to con- 
duct safely any fault current likely to be imposed. 

250.92 Services. 

(A) Bonding of Services. The non-current-carrying metal 
parts of equipment indicated in 250.92(A)(1), (2), and (3) 
shall be effectively bonded together. 

(1) The service raceways, cable trays, cablebus framework, 
auxiliary gutters, or service cable armor or sheath ex- 
cept as permitted in 250.84. 

(2) All service enclosures containing service conductors, 
including meter fittings, boxes, or the like, interposed 
in the service raceway or armor. 

(3) Any metallic raceway or armor enclosing a grounding 
electrode conductor as specified in 250.64(B). Bonding 
shall apply at each end and to all intervening raceways, 
boxes, and enclosures between the service equipment 
and the grounding electrode. 



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ARTICLE 250 — GROUNDING 



70-109 



(B) Method of Bonding at the Service. Electrical conti- 
nuity at service equipment, service raceways, and service 
conductor enclosures shall be ensured by one of the follow- 
ing methods: 

(1) Bonding equipment to the grounded service conductor 
in a manner provided in 250.8 

(2) Connections utilizing threaded couplings or threaded 
bosses on enclosures where made up wrenchtight 

(3) Threadless couplings and connectors where made up 
tight for metal raceways and metal-clad cables 

(4) Other approved devices, such as bonding-type locknuts 
and bushings 

Bonding jumpers meeting the other requirements of this 
article shall be used around concentric or eccentric knock- 
outs that are punched or otherwise formed so as to impair 
the electrical connection to ground. Standard locknuts or 
bushings shall not be the sole means for the bonding re- 
quired by this section. 

250.94 Bonding for Other Systems. An accessible means 
external to enclosures for connecting intersystem bonding 
and grounding conductors shall be provided at the service 
equipment and at the disconnecting means for any addi- 
tional buildings or structures by at least one of the follow- 
ing means: 

(1) Exposed nonflexible metallic raceways 

(2) Exposed grounding electrode conductor 

(3) Approved means for the external connection of a cop- 
per or other corrosion-resistant bonding or grounding 
conductor to the grounded raceway or equipment 

FPN No. 1: A 6 AWG copper conductor with one end 
bonded to the grounded nonflexible metallic raceway or 
equipment and with 150 mm (6 in.) or more of the other 
end made accessible on the outside wall is an example of 
the approved means covered in 250.94(3). 

FPN No. 2: See 800.40, 810.21, and 820.40 for bonding 
and grounding requirements for communications circuits, 
radio and television equipment, and CATV circuits. 

250.96 Bonding Other Enclosures. 

(A) General. Metal raceways, cable trays, cable armor, 
cable sheath, enclosures, frames, fittings, and other metal 
non-current-carrying parts that are to serve as grounding 
conductors, with or without the use of supplementary 
equipment grounding conductors, shall be effectively 
bonded where necessary to ensure electrical continuity and 
the capacity to conduct safely any fault current likely to be 
imposed on them. Any nonconductive paint, enamel, or 
similar coating shall be removed at threads, contact points, 
and contact surfaces or be connected by means of fittings 
designed so as to make such removal unnecessary. 

(B) Isolated Grounding Circuits. Where required for the 
reduction of electrical noise (electromagnetic interference) 



on the grounding circuit, an equipment enclosure supplied 
by a branch circuit shall be permitted to be isolated from a 
raceway containing circuits supplying only that equipment 
by one or more listed nonmetallic raceway fittings located 
at the point of attachment of the raceway to the equipment 
enclosure. The metal raceway shall comply with provisions 
of this article and shall be supplemented by an internal 
insulated equipment grounding conductor installed in ac- 
cordance with 250.146(D) to ground the equipment enclo- 
sure. 

FPN: Use of an isolated equipment grounding conductor 
does not relieve the requirement for grounding the raceway 
system. 

250.97 Bonding for Over 250 Volts. For circuits of over 
250 volts to ground, the electrical continuity of metal race- 
ways and cables with metal sheaths that contain any con- 
ductor other than service conductors shall be ensured by^ 
one or more of the methods specified for services in 
250.92(B), except for (1). 

Exception: Where oversized, concentric, or eccentric 
knockouts are not encountered, or where a box or enclosure 
with concentric or eccentric knockouts is listed for the pur- 
pose, the following methods shall be permitted: 

(a) Threadless couplings and connectors for cables with 
metal sheaths 

(b) Two locknuts, on rigid metal conduit or intermediate 
metal conduit, one inside and one outside of boxes and 
cabinets 

(c) Fittings with shoulders that seat firmly against the box 
or cabinet, such as electrical metallic tubing connec- 
tors, flexible metal conduit connectors, and cable con- 
nectors, with one locknut on the inside of boxes and 
cabinets 

(d) Listed fittings that are identified for the purpose 

250.98 Bonding Loosely Jointed Metal Raceways. 

Expansion fittings and telescoping sections of metal race- 
ways shall be made electrically continuous by equipment 
bonding jumpers or other means. 

250.100 Bonding in Hazardous (Classified) Locations. 

Regardless of the voltage of the electrical system, the elec- 
trical continuity of non-current-carrying metal parts of 
equipment, raceways, and other enclosures in any hazard- 
ous (classified) location as defined in Article 500 shall be 
ensured by any of the methods specified for services in 
250.92(B) that are approved for the wiring method used. 

250.102 Equipment Bonding Junipers. 

(A) Material. Equipment bonding jumpers shall be of cop- 
per or other corrosion-resistant material. A bonding jumper 
shall be a wire, bus, screw, or similar suitable conductor. 



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2002 Edition 



70-110 



ARTICLE 250 — GROUNDING 



(B) Attachment. Equipment bonding jumpers shall be at- 
tached in the manner specified by the applicable provisions 
of 250.8 for circuits and equipment and by 250.70 for 
grounding electrodes. 

(C) Size — Equipment Bonding Jumper on Supply Side 
of Service. The bonding jumper shall not be smaller than 
the sizes shown in Table 250.66 for grounding electrode 
conductors. Where the service-entrance phase conductors 
are larger than 1100 kcmil copper or 1750 kcmil aluminum, 
the bonding jumper shall have an area not less than 
12 x /2 percent of the area of the largest phase conductor 
except that, where the phase conductors and the bonding 
jumper are of different materials (copper or aluminum), the 
minimum size of the bonding jumper shall be based on the 
assumed use of phase conductors of the same material as 
the bonding jumper and with an ampacity equivalent to that 
of the installed phase conductors. Where the service- 
entrance conductors are paralleled in two or more raceways 
or cables, the equipment bonding jumper, where routed 
with the raceways or cables, shall be run in parallel. The 
size of the bonding jumper for each raceway or cable shall 
be based on the size of the service-entrance conductors in 
each raceway or cable. 

The bonding jumper for a grounding electrode conduc- 
tor raceway or cable armor as covered in 250.64(E) shall be 
the same size or larger than the required enclosed ground- 
ing electrode conductor. 

(D) Size — Equipment Bonding Jumper on Load Side 
of Service. The equipment bonding jumper on the load side 
of the service overcurrent devices shall be sized, as a mini- 
mum, in accordance with the sizes listed in Table 250.122, 
but shall not be required to be larger than the largest un- 
grounded circuit conductors supplying the equipment and 
shall not be smaller than 14 AWG. 

A single common continuous equipment bonding 
jumper shall be permitted to bond two or more raceways or 
cables where the bonding jumper is sized in accordance 
with Table 250.122 for the largest overcurrent device sup- 
plying circuits therein. 

(E) Installation. The equipment bonding jumper shall be 
permitted to be installed inside or outside of a raceway or 
enclosure. Where installed on the outside, the length of the 
equipment bonding jumper shall not exceed 1.8 m (6 ft) 
and shall be routed with the raceway or enclosure. Where 
installed inside of a raceway, the equipment bonding 
jumper shall comply with the requirements of 250.119 and 
250.148. 

Exception: An equipment bonding jumper longer than 1.8 
m (6 ft) shall be permitted at outside pole locations for the 
purpose of bonding or grounding isolated sections of metal 
raceways or elbows installed in exposed risers of metal 
conduit or other metal raceway. 



250.104 Bonding of Piping Systems and Exposed Struc- 
tural Steel. 

(A) Metal Water Piping. The metal water piping system 
shall be bonded as required in (1), (2), (3), or (4) of this 
section. The bonding jumper(s) shall be installed in accor- 
dance with 250.64(A), (B), and (E). The points of attach- 
ment of the bonding jumper(s) shall be accessible. 

(1) General. Metal water piping system(s) installed in or 
attached to a building or structure shall be bonded to the 
service equipment enclosure, the grounded conductor at the 
service, the grounding electrode conductor where of suffi- 
cient size, or to the one or more grounding electrodes used. 
The bonding jumper(s) shall be sized in accordance with 
Table 250.66 except as permitted in 250.104(A)(2) and 
(A)(3). 

(2) Buildings of Multiple Occupancy. In buildings of 
multiple occupancy where the metal water piping system(s) 
installed in or attached to a building or structure for the 
individual occupancies is metallically isolated from all 
other occupancies by use of nonmetallic water piping, the 
metal water piping system(s) for each occupancy shall be 
permitted to be bonded to the equipment grounding termi- 
nal of the panelboard or switchboard enclosure (other than 
service equipment) supplying that occupancy. The bonding 
jumper shall be sized in accordance with Table 250.122. 

(3) Multiple Buildings or Structures Supplied from a 
Common Service. The metal water piping system(s) in- 
stalled in or attached to a building or structure shall be 
bonded to the building or structure disconnecting means 
enclosure where located at the building or structure, to the 
equipment grounding conductor run with the supply con- 
ductors, or to the one or more grounding electrodes used. 
The bonding jumper(s) shall be sized in accordance with 
250.66, based on the size of the feeder or branch circuit 
conductors that supply the building. The bonding jumper 
shall not be required to be larger than the largest un- 
grounded feeder or branch circuit conductor supplying the 
building. 

(4) Separately Derived Systems. The grounded conductor 
of each separately derived system shall be bonded to the 
nearest available point of the interior metal water piping 
system(s) in the area served by each separately derived 
system. This connection shall be made at the same point on 
the separately derived system where the grounding elec- 
trode conductor is connected. Each bonding jumper shall be 
sized in accordance with Table 250.66. 

Exception: A separate water piping bonding jumper shall 
not be required where the effectively grounded metal frame 
of a building or structure is used as the grounding electrode 
for a separately derived system and is bonded to the metal- 



2002 Edition 



NATIONAL ELECTRICAL CODE 



ARTICLE 250 — GROUNDING 



70-111 



lie water piping in the area served by the separately de- 
rived system. 

(B) Other Metal Piping. Where installed in or attached to 
a building or structure, metal piping system(s), including 
gas piping, that may become energized shall be bonded to 
the service equipment enclosure, the grounded conductor at 
the service, the grounding electrode conductor where of 
sufficient size, or to the one or more grounding electrodes 
used. The bonding jumper(s) shall be sized in accordance 
with 250.122 using the rating of the circuit that may ener- 
gize the piping system(s). The equipment grounding con- 
ductor for the circuit that may energize the piping shall be 
permitted to serve as the bonding means. The points of 
attachment of the bonding jumper(s) shall be accessible. 

FPN: Bonding all piping and metal air ducts within the 
premises will provide additional safety. 

(C) Structural Steel. Exposed structural steel that is inter- 
connected to form a steel building frame and is not inten- 
tionally grounded and may become energized shall be 
bonded to the service equipment enclosure, the grounded 
conductor at the service, the grounding electrode conductor 
where of sufficient size, or the one or more grounding elec- 
trodes used. The bonding jumper(s) shall be sized in accor- 
dance with Table 250.66 and installed in accordance with 
250.64(A), (B), and (E). The points of attachment of the 
bonding jumper(s) shall be accessible. 

250.106 Lightning Protection Systems. The lightning 
protection system ground terminals shall be bonded to the 
building or structure grounding electrode system. 

FPN No. 1: See 250.60 for use of air terminals. For further 
information, see NFPA 780-1997, Standard for the Instal- 
lation of Lightning Protection Systems, which contains de- 
tailed information on grounding, bonding, and spacing 
from lightning protection systems. 

FPN No. 2: Metal raceways, enclosures, frames, and other 
non-current-carrying metal parts of electric equipment in- 
stalled on a building equipped with a lightning protection 
system may require bonding or spacing from the lightning 
protection conductors in accordance with NFPA 780-1997, 
Standard for the Installation of Lightning Protection Sys- 
tems. Separation from lightning protection conductors is 
typically 1.8 m (6 ft) through air or 900 mm (3 ft) through 
dense materials such as concrete, brick, or wood. 



VI. Equipment Grounding and Equipment Grounding 
Conductors 

250.110 Equipment Fastened in Place or Connected by 
Permanent Wiring Methods (Fixed). Exposed non- 
current-carrying metal parts of fixed equipment likely to 
become energized shall be grounded under any of the fol- 
lowing conditions: 



(1) Where within 2.5 m (8 ft) vertically or 1.5 m (5 ft) 
horizontally of ground or grounded metal objects and 
subject to contact by persons 

(2) Where located in a wet or damp location and not iso- 
lated 

(3) Where in electrical contact with metal 

(4) Where in a hazardous (classified) location as covered 
by Articles 500 through 517 

(5) Where supplied by a metal-clad, metal-sheathed, metal- 
raceway, or other wiring method that provides an 
equipment ground, except as permitted by 250.86, Ex- 
ception No. 2, for short sections of metal enclosures 

(6) Where equipment operates with any terminal at over 
150 volts to ground 

Exception No. 1: Metal frames of electrically heated appli- 
ances, exempted by special permission, in which case the 
frames shall be permanently and effectively insulated from 
ground. 

Exception No. 2: Distribution apparatus, such as trans- 
former and capacitor cases, mounted on wooden poles, at a 
height exceeding 2.5 m (8 ft) above ground or grade level. 

Exception No. 3: Listed equipment protected by a system of 
double insulation, or its equivalent, shall not be required to 
be grounded. Where such a system is employed, the equip- 
ment shall be distinctively marked. 

250.112 Fastened in Place or Connected by Permanent 
Wiring Methods (Fixed) — Specific. Exposed, non- 
current-carrying metal parts of the kinds of equipment de- 
scribed in 250.112(A) through (K), and non-current- 
carrying metal parts of equipment and enclosures described 
in 250.1 12(L) and (M), shall be grounded regardless of 
voltage. 

(A) Switchboard Frames and Structures. Switchboard 
frames and structures supporting switching equipment, ex- 
cept frames of 2-wire dc switchboards where effectively 
insulated from ground. 

(B) Pipe Organs. Generator and motor frames in an elec- 
trically operated pipe organ, unless effectively insulated 
from ground and the motor driving it. 

(C) Motor Frames. Motor frames, as provided by 
430.142. 

(D) Enclosures for Motor Controllers. Enclosures for 
motor controllers unless attached to ungrounded portable 
equipment. 

(E) Elevators and Cranes. Electric equipment for eleva- 
tors and cranes. 

(F) Garages, Theaters, and Motion Picture Studios. 

Electric equipment in commercial garages, theaters, and 



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ARTICLE 250 — GROUNDING 



motion picture studios, except pendant landholders sup- 
plied by circuits not over 150 volts to ground. 

(G) Electric Signs. Electric signs, outline lighting, and as- 
sociated equipment as provided in Article 600. 

(H) Motion Picture Projection Equipment. Motion pic- 
ture projection equipment. 

(I) Power-Limited Remote-Control, Signaling, and Fire 
Alarm Circuits. Equipment supplied by Class 1 power- 
limited circuits and Class 1, Class 2, and Class 3 remote- 
control and signaling circuits, and by fire alarm circuits, 
shall be grounded where system grounding is required by 
Part II or Part VIII of this article. 

(J) Luminaires (Lighting Fixtures). Luminaires (lighting 
fixtures) as provided in Part V of Article 410. 

(K) Skid Mounted Equipment. Permanently mounted 
electrical equipment and skids shall be grounded with an 
equipment bonding jumper sized as required by 250.122. 

(L) Motor-Operated Water Pumps. Motor-operated wa- 
ter pumps, including the submersible type. 

(M) Metal Well Casings. Where a submersible pump is 
used in a metal well casing, the well casing shall be bonded 
to the pump circuit equipment grounding conductor. 

250.114 Equipment Connected by Cord and Plug. 

Under any of the conditions described in (1) through (4), 
exposed non-current-carrying metal parts of cord-and- 
plug-connected equipment likely to become energized shall 
be grounded. 

Exception: Listed tools, listed appliances, and listed equip- 
ment covered in (2) through (4) shall not be required to be 
grounded where protected by a system of double insulation 
or its equivalent. Double insulated equipment shall be dis- 
tinctively marked. 

(1) In hazardous (classified) locations (see Articles 500 
through 517) 

(2) Where operated at over 150 volts to ground 

Exception No. 1: Motors, where guarded, shall not be re- 
quired to be grounded. 

Exception No. 2: Metal frames of electrically heated appli- 
ances, exempted by special permission, shall not be re- 
quired to be grounded, in which case the frames shall be 
permanently and effectively insulated from ground. 

(3) In residential occupancies: 

a. Refrigerators, freezers, and air conditioners 

b. Clothes-washing, clothes-drying, dish-washing ma- 
chines; kitchen waste disposers; information tech- 



nology equipment; sump pumps and electrical 
aquarium equipment 

c. Hand-held motor-operated tools, stationary and 
fixed motor-operated tools, light industrial motor- 
operated tools 

d. Motor-operated appliances of the following types: 
hedge clippers, lawn mowers, snow blowers, and 
wet scrubbers 

e. Portable handlamps 

(4) In other than residential occupancies: 

a. Refrigerators, freezers, and air conditioners 

b. Clothes-washing, clothes-drying, dish-washing ma- 
chines; information technology equipment; sump 
pumps and electrical aquarium equipment 

c. Hand-held motor-operated tools, stationary and 
fixed motor-operated tools, light industrial motor- 
operated tools 

d. Motor-operated appliances of the following types: 
hedge clippers, lawn mowers, snow blowers, and 
wet scrubbers 

e. Portable handlamps 

f. Cord-and-plug-connected appliances used in damp 
or wet locations or by persons standing on the 
ground or on metal floors or working inside of metal 
tanks or boilers 

g. Tools likely to be used in wet or conductive loca- 
tions 

Exception: Tools and portable handlamps likely to be used 
in wet or conductive locations shall not be required to be 
grounded where supplied through an isolating transformer 
with an ungrounded secondary of not over 50 volts. 

250.116 Nonelectric Equipment. The metal parts of non- 
electric equipment described in this section shall be 
grounded. 

(1) Frames and tracks of electrically operated cranes and 
hoists 

(2) Frames of nonelectrically driven elevator cars to which 
electric conductors are attached 

(3) Hand-operated metal shifting ropes or cables of electric 
elevators 

FPN: Where extensive metal in or on buildings may be- 
come energized and is subject to personal contact, adequate 
bonding and grounding will provide additional safety. 

250.118 Types of Equipment Grounding Conductors. 

The equipment grounding conductor run with or enclosing 
the circuit conductors shall be one or more or a combina- 
tion of the following: 

(1) A copper, aluminum, or copper-clad aluminum con- 
ductor. This conductor shall be solid or stranded; in- 
sulated, covered, or bare; and in the form of a wire or 
a busbar of any shape. 



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ARTICLE 250 — GROUNDING 



70-113 



(2) Rigid metal conduit. 

(3) Intermediate metal conduit. 

(4) Electrical metallic tubing. 

(5) Flexible metal conduit where both the conduit and 
fittings are listed for grounding. 

(6) Listed flexible metal conduit that is not listed for 
grounding, meeting all the following conditions: 

a. The conduit is terminated in fittings listed for 
grounding. 

b. The circuit conductors contained in the conduit are 
protected by overcurrent devices rated at 20 am- 
peres or less. 

c. The combined length of flexible metal conduit and 
flexible metallic tubing and liquidtight flexible 
metal conduit in the same ground return path does 
not exceed 1.8 m (6 ft). 

d. The conduit is not installed for flexibility. 

(7) Listed liquidtight flexible metal conduit meeting all 
the following conditions: 

a. The conduit is terminated in fittings listed for 
grounding. 

b. For metric designators 12 through 16 (trade sizes 
3 /s through Vi), the circuit conductors contained in 
the conduit are protected by overcurrent devices 
rated at 20 amperes or less. 

c. For metric designators 21 through 35 (trade sizes 
3 A through VA), the circuit conductors contained in 
the conduit are protected by overcurrent devices 
rated not more than 60 amperes and there is no 
flexible metal conduit, flexible metallic tubing, or 
liquidtight flexible metal conduit in trade sizes 
metric designators 12 through 16 (trade sizes 3 /s 
through Vi) in the grounding path. 

d. The combined length of flexible metal conduit and 
flexible metallic tubing and liquidtight flexible 
metal conduit in the same ground return path does 
not exceed 1.8 m (6 ft). 

e. The conduit is not installed for flexibility. 

(8) Flexible metallic tubing where the tubing is termi- 
nated in fittings listed for grounding and meeting the 
following conditions: 

a. The circuit conductors contained in the tubing are 
protected by overcurrent devices rated at 20 am- 
peres or less. 

b. The combined length of flexible metal conduit and 
flexible metallic tubing and liquidtight flexible 
metal conduit in the same ground return path does 
not exceed 1.8 m (6 ft). 

(9) Armor of Type AC cable as provided in 320.108. 
(10) The copper sheath of mineral-insulated, metal- 
sheathed cable. 



(11) Type MC cable where listed and identified for ground- 
ing in accordance with the following: 

a. The combined metallic sheath and grounding con- 
ductor of interlocked metal tape-type MC cable 

b. The metallic sheath or the combined metallic 
sheath and grounding conductors of the smooth or 
corrugated tube type MC cable 

(12) Cable trays as permitted in 392.3(C) and 392.7. 

(13) Cablebus framework as permitted in 370.3. 

(14) Other electrically continuous metal raceways and aux- 
iliary gutters listed for grounding. 

250.119 Identification of Equipment Grounding 
Conductors. Unless required elsewhere in this Code, 
equipment grounding conductors shall be permitted to be 
bare, covered, or insulated. Individually covered or insu- 
lated equipment grounding conductors shall have a continu- 
ous outer finish that is either green or green with one or 
more yellow stripes except as permitted in this section. 

(A) Conductors Larger Than 6 AWG. An insulated or 
covered conductor larger than 6 AWG copper or aluminum 
shall be permitted, at the time of installation, to be perma- 
nently identified as an equipment grounding conductor at 
each end and at every point where the conductor is acces- 
sible. Identification shall encircle the conductor and shall 
be accomplished by one of the following: 

(1) Stripping the insulation or covering from the entire ex- 
posed length 

(2) Coloring the exposed insulation or covering green 

(3) Marking the exposed insulation or covering with green 
tape or green adhesive labels 

(B) Multiconductor Cable. Where the conditions of 
maintenance and supervision ensure that only qualified per- 
sons service the installation, one or more insulated conduc- 
tors in a multiconductor cable, at the time of installation, 
shall be permitted to be permanently identified as equip- 
ment grounding conductors at each end and at every point 
where the conductors are accessible by one of the following 
means: 

(1) Stripping the insulation from the entire exposed length 

(2) Coloring the exposed insulation green 

(3) Marking the exposed insulation with green tape or 
green adhesive labels 

(C) Flexible Cord. An uninsulated equipment grounding 
conductor shall be permitted, but, if individually covered, 
the covering shall have a continuous outer finish that is 
either green or green with one or more yellow stripes. 

250.120 Equipment Grounding Conductor Installation. 

An equipment grounding conductor shall be installed in 
accordance with 250.120(A), (B), and (C). 



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ARTICLE 250 — GROUNDING 



(A) Raceway, Cable Trays, Cable Armor, Cablebus, or 
Cable Sheaths. Where it consists of a raceway, cable tray, 
cable armor, cablebus framework, or cable sheath or where 
it is a wire within a raceway or cable, it shall be installed in 
accordance with the applicable provisions in this Code us- 
ing fittings for joints and terminations approved for use 
with the type raceway or cable used. All connections, 
joints, and fittings shall be made tight using suitable tools. 

(B) Aluminum and Copper-Clad Aluminum Conductors. 

Equipment grounding conductors of bare or insulated alu- 
minum or copper-clad aluminum shall be permitted. Bare 
conductors shall not come in direct contact with masonry or 
the earth or where subject to corrosive conditions. Alumi- 
num or copper-clad aluminum conductors shall not be ter- 
minated within 450 mm (18 in.) of the earth. 

(C) Equipment Grounding Conductors Smaller Than 

6 AWG. Equipment grounding conductors smaller than 6 
AWG shall be protected from physical damage by a race- 
way or cable armor except where run in hollow spaces of 
walls or partitions, where not subject to physical damage, 
or where protected from physical damage. 



than 18 AWG copper and not smaller than the circuit con- 
ductors. 

(F) Conductors in Parallel. Where conductors are run in 
parallel in multiple raceways or cables as permitted in 
310.4, the equipment grounding conductors, where used, 
shall be run in parallel in each raceway or cable. One of the 
methods in 250.122(F)(1) or (2) shall be used to ensure the 
equipment grounding conductors are protected. 

(1) Each parallel equipment grounding conductor shall be 
sized on the basis of the ampere rating of the overcurrent 
device protecting the circuit conductors in the raceway or 
cable in accordance with Table 250.122. 

(2) Where ground-fault protection of equipment is installed, 
each parallel equipment grounding conductor in a multi- 
conductor cable shall be permitted to be sized in accor- 
dance with Table 250.122 on the basis of the trip rating of 
the ground-fault protection where the following conditions 
are met: 

(1) Conditions of maintenance and supervision ensure that 
only qualified persons will service the installation. 



250.122 Size of Equipment Grounding Conductors. 

(A) General. Copper, aluminum, or copper-clad aluminum 
equipment grounding conductors of the wire type shall not 
be smaller than shown in Table 250.122 but shall not be 
required to be larger than the circuit conductors supplying 
the equipment. Where a raceway or a cable armor or sheath 
is used as the equipment grounding conductor, as provided 
in 250.118 and 250.134(A), it shall comply with 
250.4(A)(5) or 250.4(B)(4). 

(B) Increased in Size. Where ungrounded conductors are 
increased in size, equipment grounding conductors, where 
installed, shall be increased in size proportionately accord- 
ing to circular mil area of the ungrounded conductors. 

(C) Multiple Circuits. Where a single equipment ground- 
ing conductor is run with multiple circuits in the same 
raceway or cable, it shall be sized for the largest overcur- 
rent device protecting conductors in the raceway or cable. 

(D) Motor Circuits. Where the overcurrent device con- 
sists of an instantaneous trip circuit breaker or a motor 
short-circuit protector, as allowed in 430.52, the equipment 
grounding conductor size shall be permitted to be based on 
the rating of the motor overload protective device but not 
less than the size shown in Table 250.122. 

(E) Flexible Cord and Fixture Wire. Equipment ground- 
ing conductors that are part of flexible cords or used with 
fixture wires in accordance with 240.5 shall be not smaller 



Table 250.122 Minimum Size Equipment Grounding 
Conductors for Grounding Raceway and Equipment 



Rating or Setting of 
Automatic Overcurrent 


Size (AWG 


or kcmil) 


Device in Circuit Ahead 






of Equipment, Conduit, 




Aluminum or 


etc., Not Exceeding 




Copper-Clad 


(Amperes) 


Copper 


Aluminum* 


15 


14 


12 


20 


12 


10 


30 


10 


8 


40 


10 


8 


60 


10 


8 


100 


8 


6 


200 


6 


4 


300 


4 


2 


400 


3 


1 


500 


2 


1/0 


600 


1 


2/0 


800 


1/0 


3/0 


1000 


2/0 


4/0 


1200 


3/0 


250 


1600 


4/0 


350 


2000 


250 


400 


2500 


350 


600 


3000 


400 


600 


4000 


500 


800 


5000 


700 


1200 


6000 


800 


1200 



Note: Where necessary to comply with 250.4(A)(5) or 250.4(B)(4), 
the equipment grounding conductor shall be sized larger than given in 
this table. 
*See installation restrictions in 250.120. 



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ARTICLE 250 — GROUNDING 



70-115 



(2) The ground-fault protection equipment is set to trip at 
not more than the ampacity of a single ungrounded 
conductor of one of the cables in parallel. 

(3) The ground-fault protection is listed for the purpose. 

250.124 Equipment Grounding Conductor Continuity. 

(A) Separable Connections. Separable connections such 
as those provided in drawout equipment or attachment 
plugs and mating connectors and receptacles shall provide 
for first-make, last-break of the equipment grounding con- 
ductor. First-make, last-break shall not be required where 
interlocked equipment, plugs, receptacles, and connectors 
preclude energization without grounding continuity. 

(B) Switches. No automatic cutout or switch shall be 
placed in the equipment grounding conductor of a premises 
wiring system unless the opening of the cutout or switch 
disconnects all sources of energy. 

250.126 Identification of Wiring Device Terminals. The 

terminal for the connection of the equipment grounding 
conductor shall be identified by one of the following: 

(1) A green, not readily removable terminal screw with a 
hexagonal head. 

(2) A green, hexagonal, not readily removable terminal 
nut. 

(3) A green pressure wire connector. If the terminal for the 
grounding conductor is not visible, the conductor en- 
trance hole shall be marked with the word green or 
ground, the letters G or GR or the grounding symbol 
shown in Figure 250.126, or otherwise identified by a 
distinctive green color. If the terminal for the equip- 
ment grounding conductor is readily removable, the 
area adjacent to the terminal shall be similarly marked. 



Figure 250.126 Grounding symbol. 



VII. Methods of Equipment Grounding 

250.130 Equipment Grounding Conductor Connec- 
tions. Equipment grounding conductor connections at the 
source of separately derived systems shall be made in ac- 
cordance with 250.30(A)(1). Equipment grounding conduc- 
tor connections at service equipment shall be made as in- 
dicated in 250.130(A) or (B). For replacement of non- 
grounding-type receptacles with grounding-type receptacles 
and for branch-circuit extensions only in existing installa- 
tions that do not have an equipment grounding conductor in 
the branch circuit, connections shall be permitted as indi- 
cated in 250.130(C). 



(A) For Grounded Systems. The connection shall be 
made by bonding the equipment grounding conductor to the 
grounded service conductor and the grounding electrode 
conductor. 

(B) For Ungrounded Systems. The connection shall be 
made by bonding the equipment grounding conductor to the 
grounding electrode conductor. 

(C) Nongrounding Receptacle Replacement or Branch 
Circuit Extensions. The equipment grounding conductor 
of a grounding-type receptacle or a branch-circuit extension 
shall be permitted to be connected to any of the following: 

(1) Any accessible point on the grounding electrode sys- 
tem as described in 250.50 

(2) Any accessible point on the grounding electrode con- 
ductor 

(3) The equipment grounding terminal bar within the en- 
closure where the branch circuit for the receptacle or 
branch circuit originates 

(4) For grounded systems, the grounded service conductor 
within the service equipment enclosure 

(5) For ungrounded systems, the grounding terminal bar 
within the service equipment enclosure 

FPN: See 406.3(D) for the use of a ground-fault circuit- 
interrupting type of receptacle. 

250.132 Short Sections of Raceway. Isolated sections of 
metal raceway or cable armor, where required to be 
grounded, shall be grounded in accordance with 250.134. 

250.134 Equipment Fastened in Place or Connected by 
Permanent Wiring Methods (Fixed) — Grounding. 

Unless grounded by connection to the grounded circuit con- 
ductor as permitted by 250.32, 250.140, and 250.142, non- 
current-carrying metal parts of equipment, raceways, and 
other enclosures, if grounded, shall be grounded by one of 
the following methods. 

(A) Equipment Grounding Conductor Types. By any of 

the equipment grounding conductors permitted by 250.118. 

(B) With Circuit Conductors. By an equipment ground- 
ing conductor contained within the same raceway, cable, or 
otherwise run with the circuit conductors. 

Exception No. 1: As provided in 250.130(C), the equip- 
ment grounding conductor shall be permitted to be run 
separately from the circuit conductors. 

Exception No. 2: For dc circuits, the equipment grounding 
conductor shall be permitted to be run separately from the 
circuit conductors. 

FPN No. 1: See 250.102 and 250.168 for equipment bond- 
ing jumper requirements. 



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ARTICLE 250 — GROUNDING 



FPN No. 2: See 400.7 for use of cords for fixed equipment. 

250.136 Equipment Considered Effectively Grounded. 

Under the conditions specified in 250.136(A) and (B), the 
non-current-carrying metal parts of the equipment shall be 
considered effectively grounded. 

(A) Equipment Secured to Grounded Metal Supports. 

Electrical equipment secured to and in electrical contact 
with a metal rack or structure provided for its support and 
grounded by one of the means indicated in 250.134. The 
structural metal frame of a building shall not be used as the 
required equipment grounding conductor for ac equipment. 

(B) Metal Car Frames. Metal car frames supported by 
metal hoisting cables attached to or running over metal 
sheaves or drums of elevator machines that are grounded 
by one of the methods indicated in 250.134. 

250.138 Cord-and-Plug-Connected Equipment. Non- 
current-carrying metal parts of cord-and-plug-connected 
equipment, if grounded, shall be grounded by one of the 
methods in 250.138(A) or (B). 

(A) By Means of an Equipment Grounding Conductor. 

By means of an equipment grounding conductor run with 
the power supply conductors in a cable assembly or flexible 
cord properly terminated in a grounding-type attachment 
plug with one fixed grounding contact. 

Exception: The grounding contacting pole of grounding- 
type plug-in ground-fault circuit interrupters shall be per- 
mitted to be of the movable, self-restoring type on circuits 
operating at not over 150 volts between any two conductors 
or over 150 volts between any conductor and ground. 

(B) By Means of a Separate Flexible Wire or Strap. By 

means of a separate flexible wire or strap, insulated or bare, 
protected as well as practicable against physical damage, 
where part of equipment. 

250.140 Frames of Ranges and Clothes Dryers. This 
section shall apply to existing branch-circuit installations 
only. New branch-circuit installations shall comply with 
250.134 and 250.138. Frames of electric ranges, wall- 
mounted ovens, counter-mounted cooking units, clothes 
dryers, and outlet or junction boxes that are part of the 
circuit for these appliances shall be grounded in the manner 
specified by 250.134 or 250.138; or, except for mobile 
homes and recreational vehicles, shall be permitted to be 
grounded to the grounded circuit conductor if all the fol- 
lowing conditions are met. 

(1) The supply circuit is 120/240- volt, single-phase, 
3- wire; or 208 Y/l 20- volt derived from a 3-phase, 
4-wire, wye-connected system. 



(2) The grounded conductor is not smaller than 10 AWG 
copper or 8 AWG aluminum. 

(3) The grounded conductor is insulated, or the grounded 
conductor is uninsulated and part of a Type SE service- 
entrance cable and the branch circuit originates at the 
service equipment. 

(4) Grounding contacts of receptacles furnished as part of 
the equipment are bonded to the equipment. 

250.142 Use of Grounded Circuit Conductor for 
Grounding Equipment. 

(A) Supply-Side Equipment. A grounded circuit conduc- 
tor shall be permitted to ground non-current-carrying metal 
parts of equipment, raceways, and other enclosures at any 
of the following locations: 

(1) On the supply side or within the enclosure of the ac 
service-disconnecting means 

(2) On the supply side or within the enclosure of the main 
disconnecting means for separate buildings as provided 
in 250.32(B) 

(3) On the supply side or within the enclosure of the main 
disconnecting means or overcurrent devices of a sepa- 
rately derived system where permitted by 250.30(A)(1) 

(B) Load-Side Equipment. Except as permitted in 
250.30(A)(1) and 250.32(B), a grounded circuit conductor 
shall not be used for grounding non-current-carrying metal 
parts of equipment on the load side of the service discon- 
necting means or on the load side of a separately derived 
system disconnecting means or the overcurrent devices for 
a separately derived system not having a main disconnect- 
ing means. 

Exception No. 1: The frames of ranges, wall-mounted ov- 
ens, counter-mounted cooking units, and clothes dryers un- 
der the conditions permitted for existing installations by 
250.140 shall be permitted to be grounded by a grounded 
circuit conductor. 

Exception No. 2: It shall be permissible to ground meter 
enclosures by connection to the grounded circuit conductor 
on the load side of the service disconnect if 

(a) No service ground-fault protection is installed, and 

(b) All meter enclosures are located near the service dis- 
connecting means, and 

(c) The size of the grounded circuit conductor is not 
smaller than the size specified in Table 250.122 for 
equipment grounding conductors. 

Exception No. 3: Direct-current systems shall be permitted 
to be grounded on the load side of the disconnecting means 
or overcurrent device in accordance with 250.164. 

Exception No. 4: Electrode-type boilers operating at over 
600 volts shall be grounded as required in 490.72(E)(1) 
and 490.74. 



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ARTICLE 250 — GROUNDING 



70-117 



250.144 Multiple Circuit Connections. Where equipment 
is required to be grounded and is supplied by separate con- 
nection to more than one circuit or grounded premises wir- 
ing system, a means for grounding shall be provided for 
each such connection as specified in 250.134 and 250.138. 

250.146 Connecting Receptacle Grounding Terminal to 
Box. An equipment bonding jumper shall be used to con- 
nect the grounding terminal of a grounding-type receptacle 
to a grounded box unless grounded as in 250.146(A) 
through (D). 

(A) Surface Mounted Box. Where the box is mounted on 
the surface, direct metal-to-metal contact between the de- 
vice yoke and the box shall be permitted to ground the 
receptacle to the box. This provision shall not apply to 
cover-mounted receptacles unless the box and cover com- 
bination are listed as providing satisfactory ground conti- 
nuity between the box and the receptacle. 

(B) Contact Devices or Yokes. Contact devices or yokes 
designed and listed for the purpose shall be permitted in 
conjunction with the supporting screws to establish the 
grounding circuit between the device yoke and flush-type 
boxes. 

(C) Floor Boxes. Floor boxes designed for and listed as 
providing satisfactory ground continuity between the box 
and the device shall be permitted. 

(D) Isolated Receptacles. Where required for the reduc- 
tion of electrical noise (electromagnetic interference) on the 
grounding circuit, a receptacle in which the grounding ter- 
minal is purposely insulated from the receptacle mounting 
means shall be permitted. The receptacle grounding termi- 
nal shall be grounded by an insulated equipment grounding 
conductor run with the circuit conductors. This grounding 
conductor shall be permitted to pass through one or more 
panelboards without connection to the panelboard ground- 
ing terminal as permitted in 408.20, Exception, so as to 
terminate within the same building or structure directly at 
an equipment grounding conductor terminal of the appli- 
cable derived system or service. 

FPN: Use of an isolated equipment grounding conductor 
does not relieve the requirement for grounding the raceway 
system and outlet box. 

250.148 Continuity and Attachment of Equipment 
Grounding Conductors to Boxes. Where circuit conduc- 
tors are spliced within a box, or terminated on equipment 
within or supported by a box, any separate equipment 
grounding conductors associated with those circuit conduc- 
tors shall be spliced or joined within the box or to the box 
with devices suitable for the use. Connections depending 
solely on solder shall not be used. Splices shall be made in 



accordance with 110.14(B) except that insulation shall not 
be required. The arrangement of grounding connections 
shall be such that the disconnection or the removal of a 
receptacle, luminaire (fixture), or other device fed from the 
box will not interfere with or interrupt the grounding con- 
tinuity. 

Exception: The equipment grounding conductor permitted 
in 250. 146(D) shall not be required to be connected to the 
other equipment grounding conductors or to the box. 

(A) Metal Boxes. A connection shall be made between the 
one or more equipment grounding conductors and a metal 
box by means of a grounding screw that shall be used for 
no other purpose or a listed grounding device. 

(B) Nonmetallic Boxes. One or more equipment ground- 
ing conductors brought into a nonmetallic outlet box shall 
be arranged so that a connection can be made to any fitting 
or device in that box requiring grounding. 

VIII. Direct-Current Systems 

250.160 General. Direct-current systems shall comply 
with Part VIII and other sections of Article 250 not specifi- 
cally intended for ac systems. 

250.162 Direct-Current Circuits and Systems to Be 
Grounded. Direct-current circuits and systems shall be 
grounded as provided for in 250.162(A) and (B). 

(A) Two-Wire, Direct-Current Systems. A 2-wire, dc 
system supplying premises wiring and operating at greater 
than 50 volts but not greater than 300 volts shall be 
grounded. 

Exception No. 1: A system equipped with a ground detec- 
tor and supplying only industrial equipment in limited ar- 
eas shall not be required to be grounded. 

Exception No. 2: A rectifier-derived dc system supplied 
from an ac system complying with 250.20 shall not be re- 
quired to be grounded. 

Exception No. 3: Direct-current fire alarm circuits having 
a maximum current of 0.030 amperes as specified in Article 
760, Part III, shall not be required to be grounded. 

(B) Three-Wire, Direct-Current Systems. The neutral 
conductor of all 3-wire, dc systems supplying premises wir- 
ing shall be grounded. 

250.164 Point of Connection for Direct-Current Sys- 
tems. 

(A) Off-Premises Source. Direct-current systems to be 
grounded and supplied from an off-premises source shall 
have the grounding connection made at one or more supply 



NATIONAL ELECTRICAL CODE 



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70-118 



ARTICLE 250 — GROUNDING 



stations. A grounding connection shall not be made at indi- 
vidual services or at any point on the premises wiring. 

(B) On-Premises Source. Where the dc system source is 
located on the premises, a grounding connection shall be 
made at one of the following: 

(1) The source 

(2) The first system disconnection means or overcurrent 
device 

(3) By other means that accomplish equivalent system pro- 
tection and that utilize equipment listed and identified 
for the use 

250.166 Size of Direct-Current Grounding Electrode 
Conductor. The size of the grounding electrode conductor 
for a dc system shall be as specified in 250.166(A) through 

(E). 

(A) Not Smaller Than the Neutral Conductor. Where 
the dc system consists of a 3-wire balancer set or a balancer 
winding with overcurrent protection as provided in 
445.12(D), the grounding electrode conductor shall not be 
smaller than the neutral conductor and not smaller than 8 
AWG copper or 6 AWG aluminum. 

(B) Not Smaller Than the Largest Conductor. Where the 
dc system is other than as in 250.166(A), the grounding 
electrode conductor shall not be smaller than the largest 
conductor supplied by the system, and not smaller than 8 
AWG copper or 6 AWG aluminum. 

(C) Connected to Rod, Pipe, or Plate Electrodes. Where 
connected to rod, pipe, or plate electrodes as in 
250.52(A)(5) or 250.52(A)(6), that portion of the grounding 
electrode conductor that is the sole connection to the 
grounding electrode shall not be required to be larger than 6 
AWG copper wire or 4 AWG aluminum wire. 

(D) Connected to a Concrete-Encased Electrode. Where 
connected to a concrete-encased electrode as in 
250.52(A)(3), that portion of the grounding electrode con- 
ductor that is the sole connection to the grounding electrode 
shall not be required to be larger than 4 AWG copper wire. 

(E) Connected to a Ground Ring. Where connected to a 
ground ring as in 250.52(A)(4), that portion of the ground- 
ing electrode conductor that is the sole connection to the 
grounding electrode shall not be required to be larger than 
the conductor used for the ground ring. 

250.168 Direct-Current Bonding Jumper. For dc sys- 
tems, the size of the bonding jumper shall not be smaller 
than the system grounding conductor specified in 250.166. 

250.169 Ungrounded Direct-Current Separately De- 
rived Systems. Except as otherwise permitted in 250.34 for 



portable and vehicle-mounted generators, an ungrounded 
dc separately derived system supplied from a stand-alone 
power source (such as an engine-generator set) shall have a 
grounding electrode conductor connected to an electrode 
that complies with Part III to provide for grounding of 
metal enclosures, raceways, cables, and exposed non- 
current-carrying metal parts of equipment. The grounding 
electrode conductor connection shall be to the metal enclo- 
sure at any point on the separately derived system from the 
source to the first system disconnecting means or overcur- 
rent device, or it shall be made at the source of a separately 
derived system that has no disconnecting means or overcur- 
rent devices. 

The size of the grounding electrode conductor shall be 
in accordance with 250.166. 

IX. Instruments, Meters, and Relays 

250.170 Instrument Transformer Circuits. Secondary 
circuits of current and potential instrument transformers 
shall be grounded where the primary windings are con- 
nected to circuits of 300 volts or more to ground and, where 
on switchboards, shall be grounded irrespective of voltage. 

Exception: Circuits where the primary windings are con- 
nected to circuits of less than 1000 volts with no live parts 
or wiring exposed or accessible to other than qualified 
persons. 

250.172 Instrument Transformer Cases. Cases or frames 
of instrument transformers shall be grounded where acces- 
sible to other than qualified persons. 

Exception: Cases or frames of current transformers, the 
primaries of which are not over J 50 volts to ground and 
that are used exclusively to supply current to meters. 

250.174 Cases of Instruments, Meters, and Relays Op- 
erating at Less Than 1000 Volts. Instruments, meters, and 
relays operating with windings or working parts at less than 
1000 volts shall be grounded as specified in 250.174(A), 
(B), or (C). 

(A) Not on Switchboards. Instruments, meters, and relays 
not located on switchboards, operating with windings or 
working parts at 300 volts or more to ground, and acces- 
sible to other than qualified persons, shall have the cases 
and other exposed metal parts grounded. 

(B) On Dead-Front Switchboards. Instruments, meters, 
and relays (whether operated from current and potential 
transformers or connected directly in the circuit) on switch- 
boards having no live parts on the front of the panels shall 
have the cases grounded. 

(C) On Live-Front Switchboards. Instruments, meters, 
and relays (whether operated from current and potential 



2002 Edition 



NATIONAL ELECTRICAL CODE 



ARTICLE 250 — GROUNDING 



70-119 



transformers or connected directly in the circuit) on switch- 
boards having exposed live parts on the front of panels 
shall not have their cases grounded. Mats of insulating rub- 
ber or other suitable floor insulation shall be provided for 
the operator where the voltage to ground exceeds 150. 

250.176 Cases of Instruments, Meters, and Relays — 
Operating Voltage 1 kV and Over. Where instruments, 
meters, and relays have current-carrying parts of 1 kV and 
over to ground, they shall be isolated by elevation or pro- 
tected by suitable barriers, grounded metal, or insulating 
covers or guards. Their cases shall not be grounded. 

Exception: Cases of electrostatic ground detectors where 
the internal ground segments of the instrument are con- 
nected to the instrument case and grounded and the ground 
detector is isolated by elevation. 

250.178 Instrument Grounding Conductor. The ground- 
ing conductor for secondary circuits of instrument trans- 
formers and for instrument cases shall not be smaller than 
12 AWG copper or 10 AWG aluminum. Cases of instru- 
ment transformers, instruments, meters, and relays that are 
mounted directly on grounded metal surfaces of enclosures 
or grounded metal switchboard panels shall be considered 
to be grounded, and no additional grounding conductor 
shall be required. 

X. Grounding of Systems and Circuits of 1 kV and 
Over (High Voltage) 

250.180 General. Where high-voltage systems are 
grounded, they shall comply with all applicable provisions 
of the preceding sections of this article and with 250.182 
through 250.190, which supplement and modify the preced- 
ing sections. 

250.182 Derived Neutral Systems. A system neutral de- 
rived from a grounding transformer shall be permitted to be 
used for grounding high-voltage systems. 

250.184 Solidly Grounded Neutral Systems. 

(A) Neutral Conductor. The minimum insulation level for 
neutral conductors of solidly grounded systems shall be 600 volts. 

Exception No. 1: Bare copper conductors shall be permit- 
ted to be used for the neutral of service entrances and the 
neutral of direct-buried portions of feeders. 

Exception No. 2: Bare conductors shall be permitted for 
the neutral of overhead portions installed outdoors. 

FPN: See 225.4 for conductor covering where within 3.0 m 
(10 ft) of any building or other structure. 



(B) Multiple Grounding. The neutral of a solidly 
grounded neutral system shall be permitted to be grounded 
at more than one point. Grounding shall be permitted at one 
or more of the following locations: 

(1) Transformers supplying conductors to a building or 
other structure 

(2) Underground circuits where the neutral is exposed 

(3) Overhead circuits installed outdoors 

(C) Neutral Grounding Conductor. The neutral ground- 
ing conductor shall be permitted to be a bare conductor if 
isolated from phase conductors and protected from physical 
damage. 

(D) Multigrounded Neutral Conductor. Where a multi- 
grounded neutral system is used, the following shall apply: 

(1) The multigrounded neutral conductor shall be of suffi- 
cient ampacity for the load imposed on the conductor 
but not less than 33 ] /3 percent of the ampacity of the 
phase conductors. 

Exception: In industrial and commercial premises under 
engineering supervision, it shall be permissible to size the 
ampacity of the neutral conductor to not less than 20 per- 
cent of the ampacity of the phase conductor. 

(2) The multigrounded neutral conductor shall be grounded 
at each transformer and at other additional locations by 
connection to a made or existing electrode. 

(3) At least one grounding electrode shall be installed and 
connected to the multigrounded neutral circuit conduc- 
tor every 400 m (1300 ft). 

(4) The maximum distance between any two adjacent elec- 
trodes shall not be more than 400 m (1300 ft). 

(5) In a multigrounded shielded cable system, the shielding 
shall be grounded at each cable joint that is exposed to 
personnel contact. 

250.186 Impedance Grounded Neutral Systems. 

Impedance grounded neutral systems in which a grounding 
impedance, usually a resistor, limits the ground-fault cur- 
rent, shall be permitted where all of the following condi- 
tions are met. 

(1) The conditions of maintenance and supervision ensure 
that only qualified persons will service the installation. 

(2) Ground detectors are installed on the system. 

(3) Line-to-neutral loads are not served. 

Impedance grounded neutral systems shall comply with 
the provisions of 250.186(A) through (D). 

(A) Location. The grounding impedance shall be inserted 
in the grounding conductor between the grounding elec- 



NATIONAL ELECTRICAL CODE 



2002 Edition 



70-120 



ARTICLE 280 — SURGE ARRESTERS 



trode of the supply system and the neutral point of the 
supply transformer or generator. 

(B) Identified and Insulated. The neutral conductor of an 
impedance grounded neutral system shall be identified, as 
well as fully insulated with the same insulation as the phase 
conductors. 

(C) System Neutral Connection. The system neutral shall 
not be connected to ground, except through the neutral 
grounding impedance. 

(D) Equipment Grounding Conductors. Equipment 
grounding conductors shall be permitted to be bare and 
shall be electrically connected to the ground bus and 
grounding electrode conductor. 

250.188 Grounding of Systems Supplying Portable or 
Mobile Equipment. Systems supplying portable or mobile 
high-voltage equipment, other than substations installed on 
a temporary basis, shall comply with 250.188(A) through (F). 

(A) Portable or Mobile Equipment. Portable or mobile 
high-voltage equipment shall be supplied from a system 
having its neutral grounded through an impedance. Where a 
delta-connected high-voltage system is used to supply por- 
table or mobile equipment, a system neutral shall be de- 
rived. 

(B) Exposed Non-Current-Carrying Metal Parts. Exposed 
non-current-carrying metal parts of portable or mobile 
equipment shall be connected by an equipment grounding 
conductor to the point at which the system neutral imped- 
ance is grounded. 

(C) Ground-Fault Current. The voltage developed be- 
tween the portable or mobile equipment frame and ground 
by the flow of maximum ground-fault current shall not 
exceed 100 volts. 

(D) Ground-Fault Detection and Relaying. Ground-fault 
detection and relaying shall be provided to automatically 
de-energize any high-voltage system component that has 
developed a ground fault. The continuity of the equipment 
grounding conductor shall be continuously monitored so as 
to de-energize automatically the high-voltage circuit to the 
portable or mobile equipment upon loss of continuity of the 
equipment grounding conductor. 

(E) Isolation. The grounding electrode to which the por- 
table or mobile equipment system neutral impedance is 
connected shall be isolated from and separated in the 
ground by at least 6.0 m (20 ft) from any other system or 
equipment grounding electrode, and there shall be no direct 
connection between the grounding electrodes, such as bur- 
ied pipe and fence, and so forth. 



(F) Trailing Cable and Couplers. High-voltage trailing 
cable and couplers for interconnection of portable or mo- 
bile equipment shall meet the requirements of Part III of 
Article 400 for cables and 490.55 for couplers. 

250.190 Grounding of Equipment. All non-current- 
carrying metal parts of fixed, portable, and mobile equip- 
ment and associated fences, housings, enclosures, and sup- 
porting structures shall be grounded. 

Exception: Where isolated from ground and located so as 
to prevent any person who can make contact with ground 
from contacting such metal parts when the equipment is 
energized. 

Grounding conductors not an integral part of a cable 
assembly shall not be smaller than 6 AWG copper or 4 
AWG aluminum. 

FPN: See 250.110, Exception No. 2, for pole-mounted dis- 
tribution apparatus. 



ARTICLE 280 
Surge Arresters 

I. General 

280.1 Scope. This article covers general requirements, in- 
stallation requirements, and connection requirements for 
surge arresters installed on premises wiring systems. 

280.2 Definition. 

Surge Arrester. A protective device for limiting surge volt- 
ages by discharging or bypassing surge current, and it also 
prevents continued flow of follow current while remaining 
capable of repeating these functions. 

280.3 Number Required. Where used at a point on a cir- 
cuit, a surge arrester shall be connected to each ungrounded 
conductor. A single installation of such surge arresters shall 
be permitted to protect a number of interconnected circuits, 
provided that no circuit is exposed to surges while discon- 
nected from the surge arresters. 

280.4 Surge Arrester Selection. 

(A) Circuits of Less Than 1000 Volts. The rating of the 
surge arrester shall be equal to or greater than the maxi- 
mum continuous phase-to-ground power frequency voltage 
available at the point of application. 

Surge arresters installed on circuits of less than 1000 
volts shall be listed for the purpose. 



2002 Edition 



NATIONAL ELECTRICAL CODE 



ARTICLE 280 — SURGE ARRESTERS 



70-121 



• 



(B) Circuits of 1 kV and Over — Silicon Carbide Types. 

The rating of a silicon carbide-type surge arrester shall be 
not less than 125 percent of the maximum continuous phase- 
to-ground voltage available at the point of application. 

FPN No. 1 : For further information on surge arresters, see 
ANSI/IEEE C62.1-1989, Standard for Gapped Silicon- 
Carbide Surge Arresters for AC Power Circuits; 
ANSI/IEEE C62.2-1987, Guide for the Application of 
Gapped Silicon-Carbide Surge Arresters for Alternating- 
Current Systems; ANSI/IEEE C62.1 1-1993, Standard for 
Metal-Oxide Surge Arresters for Alternating-Current 
Power Circuits; and ANSI/IEEE C62.22-1991, Guide for 
the Application of Metal-Oxide Surge Arresters for 
Alternating-Current Systems. 

FPN No. 2: The selection of a properly rated metal oxide 
arrester is based on considerations of maximum continuous 
operating voltage and the magnitude and duration of over- 
voltages at the arrester location as affected by phase-to- 
ground faults, system grounding techniques, switching 
surges, and other causes. See the manufacturer's applica- 
tion rules for selection of the specific arrester to be used at 
a particular location. 



II. Installation 

280.11 Location. Surge arresters shall be permitted to be 
located indoors or outdoors. Surge arresters shall be made 
inaccessible to unqualified persons, unless listed for instal- 
lation in accessible locations. 

280.12 Routing of Surge Arrester Connections. The con- 
ductor used to connect the surge arrester to line or bus and 
to ground shall not be any longer than necessary and shall 
avoid unnecessary bends. 

III. Connecting Surge Arresters 

280.21 Installed at Services of Less Than 1000 Volts;. 

Line and ground connecting conductors shall not be smaller 
than 14 AWG copper or 12 AWG aluminum. The arrester 
grounding conductor shall be connected to one of the fol- 
lowing: 

(1) Grounded service conductor 

(2) Grounding electrode conductor 

(3) Grounding electrode for the service 

(4) Equipment grounding terminal in the service 
equipment 

280.22 Installed on the Load Side Services of Less Than 
1000 Volts. Line and ground connecting conductors shall 
not be smaller than 14 AWG copper or 12 AWG aluminum. 
A surge arrester shall be permitted to be connected between 
any two conductors — ungrounded conductor(s), grounded 
conductor, grounding conductor. The grounded conductor 
and the grounding conductor shall be interconnected only 
by the normal operation of the surge arrester during a surge. 



280.23 Circuits of 1 kV and Over — Surge-Arrester 
Conductors. The conductor between the surge arrester and 
the line and the surge arrester and the grounding connection 
shall not be smaller than 6 AWG copper or aluminum. 

280.24 Circuits of 1 kV and Over — Interconnections. 

The grounding conductor of a surge arrester protecting a 
transformer that supplies a secondary distribution system 
shall be interconnected as specified in 280.24(A), (B), or 
(C). 

(A) Metallic Interconnections. A metallic interconnection 
shall be made to the secondary grounded circuit conductor 
or the secondary circuit grounding conductor provided that, 
in addition to the direct grounding connection at the surge 
arrester, the following occurs: 

(1) The grounded conductor of the secondary has else- 
where a grounding connection to a continuous metal 
underground water piping system. However, in urban 
water-pipe areas where there are at least four water- 
pipe connections on the neutral and not fewer than four 
such connections in each mile of neutral, the metallic 
interconnection shall be permitted to be made to the 
secondary neutral with omission of the direct ground- 
ing connection at the surge arrester. 

(2) The grounded conductor of the secondary system is a 
part of a multiground neutral system of which the pri- 
mary neutral has at least four ground connections in 
each mile of line in addition to a ground at each 
service. 

(B) Through Spark Gap or Device. Where the surge ar- 
rester grounding conductor is not connected as in 
280.24(A) or where the secondary is not grounded as in 
280.24(A) but is otherwise grounded as in 250.52, an inter- 
connection shall be made through a spark gap or listed 
device as follows: 

(1) For ungrounded or unigrounded primary systems, the 
spark gap or listed device shall have a 60-Hz break- 
down voltage of at least twice the primary circuit volt- 
age but not necessarily more than 10 kV, and there shall 
be at least one other ground on the grounded conductor 
of the secondary that is not less than 6.0 m (20 ft) 
distant from the surge arrester grounding electrode. 

(2) For multigrounded neutral primary systems, the spark 
gap or listed device shall have a 60-Hz breakdown of 
not more than 3 kV, and there shall be at least one other 
ground on the grounded conductor of the secondary 
that is not less than 6.0 m (20 ft) distant from the surge 
arrester grounding electrode. 

(C) By Special Permission. An interconnection of the 
surge arrester ground and the secondary neutral, other than 
as provided in 280.24(A) or (B), shall be permitted to be 
made only by special permission. 



NATIONAL ELECTRICAL CODE 



2002 Edition 



70-122 



ARTICLE 285 — TRANSIENT VOLTAGE SURGE SUPPRESSORS: TVSSs 



280.25 Grounding. Except as indicated in this article, 
surge arrester grounding connections shall be made as 
specified in Article 250. Grounding conductors shall not be 
run in metal enclosures unless bonded to both ends of such 
enclosure. 



ARTICLE 285 

Transient Voltage Surge Suppressors: 

TVSSs 

I. General 

285.1 Scope. This article covers general requirements, in- 
stallation requirements, and connection requirements for 
transient voltage surge suppressors (TVSS) permanently in- 
stalled on premises wiring systems. 

285.2 Definition. 

Transient Voltage Surge Suppressor (TVSS). A protec- 
tive device for limiting transient voltages by diverting or 
limiting surge current; it also prevents continued flow of 
follow current while remaining capable of repeating these 
functions. 

285.3 Uses Not Permitted. A TVSS shall not be used in 
the following: 

(1) Circuits exceeding 600 volts 

(2) Ungrounded electrical systems as permitted in 250.21 

(3) Where the rating of the TVSS is less than the maxi- 
mum continuous phase-to-ground power frequency 
voltage available at the point of application 

FPN: For further information on TVSSs, see NEMA LS 
1-1992, Standard for Low Voltage Surge Suppression De- 
vices. The selection of a properly rated TVSS is based on 
criteria such as maximum continuous operating voltage, the 
magnitude and duration of overvoltages at the suppressor 
location as affected by phase-to-ground faults, system 
grounding techniques, and switching surges. 

285.4 Number Required. Where used at a point on a cir- 
cuit, the TVSS shall be connected to each ungrounded con- 
ductor. 

285.5 Listing. A TVSS shall be a listed device. 

285.6 Short Circuit Current Rating. The TVSS shall be 
marked with a short circuit current rating and shall not be 



installed at a point on the system where the available fault 
current is in excess of that rating. This marking requirement 
shall not apply to receptacles. 

II. Installation 

285.11 Location. TVSSs shall be permitted to be located 
indoors or outdoors and shall be made inaccessible to un- 
qualified persons, unless listed for installation in accessible 
locations. 

285.12 Routing of Connections. The conductors used to 
connect the the TVSS to the line or bus and to ground shall 
not be any longer than necessary and shall avoid unneces- 
sary bends. 

III. Connecting Transient Voltage Surge Suppressors 

285.21 Connection. Where a TVSS is installed, it shall be 
connected as follows. 

(A)) Location. 

(1)) Service Supplied Building or Structure. The tran- 
sient voltage surge suppressor shall be connected on the 
load side of a service disconnect overcurrent device re- 
quired in 230.91. 

(2)) Feeder Supplied Building or Structure. The tran- 
sient voltage surge suppressor shall be connected on the load 
side of the first overcurrent device at the building or structure. 

Exception to (1) and (2): Where the TVSS is also listed as a 
surge arrester, the connection shall be as permitted by Ar- 
ticle 280. 

(3)) Separately Derived System. The TVSS shall be con- 
nected on the load side of the first overcurrent device in a 
separately derived system. 

(B)) Conductor Size. Line and ground connecting conduc- 
tors shall not be smaller than 14 AWG copper or 12 AWG 
aluminum. 

(C)) Connection Between Conductors. A TVSS shall be 
permitted to be connected between any two conductors — 
ungrounded conductor(s), grounded conductor, grounding 
conductor. The grounded conductor and the grounding con- 
ductor shall be interconnected only by the normal operation 
of the TVSS during a surge. 

285.25 Grounding. Grounding conductors shall not be run 
in metal enclosures unless bonded to both ends of such 
enclosure. 



2002 Edition 



NATIONAL ELECTRICAL CODE 



ARTICLE 300 — WIRING METHODS 



70-123 



Chapter 3 Wiring Methods and Materials 



ARTICLE 300 
Wiring Methods 



I. General Requirements 
300.1 Scope. 

(A) All Wiring Installations. This article covers wiring 
methods for all wiring installations unless modified by 
other articles. 

(B) Integral Parts of Equipment. The provisions of this 
article are not intended to apply to the conductors that form 
an integral part of equipment, such as motors, controllers, 
motor control centers, or factory assembled control equip- 
ment or listed utilization equipment. 

(C) Metric Designators and Trade Sizes. Metric designa- 
tors and trade sizes for conduit, tubing, and associated fit- 
tings and accessories shall be as designated in Table 
300.1(C). 

Table 300.1(C) Metric Designator and Trade Sizes 



Metric Designator 


Trade Size 


12 


% 


16 


Vl 


21 


3 /4 


27 


1 


35 


l'/4 


41 


\V2 


53 


2 


63 


2'/2 


78 


3 


91 


3'/2 


103 


4 


129 


5 


155 


6 



Note: The metric designators and trade sizes are for identification 
purposes only and are not actual dimensions. 



300.2 Limitations. 

(A) Voltage. Wiring methods specified in Chapter 3 shall 
be used for 600 volts, nominal, or less where not specifi- 
cally limited in some section of Chapter 3. They shall be 
permitted for over 600 volts, nominal, where specifically 
permitted elsewhere in this Code. 

(B) Temperature. Temperature limitation of conductors 
shall be in accordance with 310.10. 



300.3 Conductors. 

(A) Single Conductors. Single conductors specified in 
Table 310.13 shall only be installed where part of a recog- 
nized wiring method of Chapter 3. 

(B) Conductors of the Same Circuit. All conductors of 
the same circuit and, where used, the grounded conductor 
and all equipment grounding conductors and bonding con- 
ductors shall be contained within the same raceway, auxil- 
iary gutter, cable tray, cablebus assembly, trench, cable, or 
cord, unless otherwise permitted in accordance with 
300.3(B)(1) through (4). 

(1) Paralleled Installations. Conductors shall be permit- 
ted to be run in parallel in accordance with the provisions 
of 310.4. The requirement to run all circuit conductors 
within the same raceway, auxiliary gutter, cable tray, 
trench, cable, or cord shall apply separately to each portion 
of the paralleled installation, and the equipment grounding 
conductors shall comply with the provisions of 250.122. 
Parallel runs in cable tray shall comply with the provisions 
of 392.8(D). 

Exception: Conductors installed in nonmetallic raceways 
run underground shall be permitted to be arranged as iso- 
lated phase installations. The raceways shall be installed in 
close proximity, and the conductors shall comply with the 
provisions of 300.20(B). 

(2) Grounding and Bonding Conductors. Equipment 
grounding conductors shall be permitted to be installed out- 
side a raceway or cable assembly where in accordance with 
the provisions of 250.130(C) for certain existing installa- 
tions or in accordance with 250.134(B), Exception No. 2, 
for dc circuits. Equipment bonding conductors shall be per- 
mitted to be installed on the outside of raceways in accor- 
dance with 250.102(E). 

(3) Nonferrous Wiring Methods. Conductors in wiring 
methods with a nonmetallic or other nonmagnetic sheath, 
where run in different raceways, auxiliary gutters, cable 
trays, trenches, cables, or cords, shall comply with the pro- 
visions of 300.20(B). Conductors in single-conductor Type 
MI cable with a nonmagnetic sheath shall comply with the 
provisions of 332.31. Conductors of single-conductor-type 
MC cable with a nonmagnetic sheath shall comply with the 
provisions of 330.31, 330.116, and 300.20(B). 

(4) Enclosures. Where an auxiliary gutter runs between a 
column-width panelboard and a pull box, and the pull box 
includes neutral terminations, the neutral conductors of cir- 
cuits supplied from the panelboard shall be permitted to 
originate in the pull box. 



NATIONAL ELECTRICAL CODE 



2002 Edition 



70-124 



ARTICLE 300 — WIRING METHODS 



(C) Conductors of Different Systems. 

(1) 600 Volts, Nominal, or Less. Conductors of circuits 
rated 600 volts, nominal, or less, ac circuits, and dc circuits 
shall be permitted to occupy the same equipment wiring 
enclosure, cable, or raceway. All conductors shall have an 
insulation rating equal to at least the maximum circuit volt- 
age applied to any conductor within the enclosure, cable, or 
raceway. 

Exception: For solar photovoltaic systems in accordance 
with 690.4(B). 

FPN: See 725.55(A) for Class 2 and Class 3 circuit 
conductors. 

(2) Over 600 Volts, Nominal. Conductors of circuits rated 
over 600 volts, nominal, shall not occupy the same equip- 
ment wiring enclosure, cable, or raceway with conductors 
of circuits rated 600 volts, nominal, or less unless otherwise 
permitted in (a) through (e). 

(a) Secondary wiring to electric-discharge lamps of 
1000 volts or less, if insulated for the secondary voltage 
involved, shall be permitted to occupy the same luminaire 
(fixture), sign, or outline lighting enclosure as the branch- 
circuit conductors. 

(b) Primary leads of electric-discharge lamp ballasts, 
insulated for the primary voltage of the ballast, where con- 
tained within the individual wiring enclosure, shall be per- 
mitted to occupy the same luminaire (fixture), sign, or out- 
line lighting enclosure as the branch-circuit conductors. 

(c) Excitation, control, relay, and ammeter conductors 
used in connection with any individual motor or starter 
shall be permitted to occupy the same enclosure as the 
motor-circuit conductors. 

(d) In motors, switchgear and control assemblies, and 
similar equipment, conductors of different voltage ratings 
shall be permitted. 

(e) In manholes, if the conductors of each system are 
permanently and effectively separated from the conductors 
of the other systems and securely fastened to racks, insula- 
tors, or other approved supports, conductors of different 
voltage ratings shall be permitted. 

Conductors having nonshielded insulation and operat- 
ing at different voltage levels shall not occupy the same 
enclosure, cable, or raceway. 

300.4 Protection Against Physical Damage. Where sub- 
ject to physical damage, conductors shall be adequately 
protected. 

(A) Cables and Raceways Through Wood Members. 

(1) Bored Holes. In both exposed and concealed locations, 
where a cable- or raceway-type wiring method is installed 



through bored holes in joists, rafters, or wood members, 
holes shall be bored so that the edge of the hole is not less 
than 32 mm (1 l A in.) from the nearest edge of the wood 
member. Where this distance cannot be maintained, the 
cable or raceway shall be protected from penetration by 
screws or nails by a steel plate or bushing, at least 1.6 mm 
('/i6 in.) thick, and of appropriate length and width installed 
to cover the area of the wiring. 

Exception: Steel plates shall not be required to protect 
rigid metal conduit, intermediate metal conduit, rigid non- 
metallic conduit, or electrical metallic tubing. 

(2) Notches in Wood. Where there is no objection because 
of weakening the building structure, in both exposed and 
concealed locations, cables or raceways shall be permitted 
to be laid in notches in wood studs, joists, rafters, or other 
wood members where the cable or raceway at those points 
is protected against nails or screws by a steel plate at least 
1.6 mm (l / ]6 in.) thick installed before the building finish is 
applied. 

Exception: Steel plates shall not be required to protect 
rigid metal conduit, intermediate metal conduit, rigid non- 
metallic conduit, or electrical metallic tubing. 

(B) Nonmetallic-Sheathed Cables and Electrical Non- 
metallic Tubing Through Metal Framing Members. 

(1) Nonmetallic-Sheathed Cable. In both exposed and 
concealed locations where nonmetallic-sheathed cables 
pass through either factory or field punched, cut, or drilled 
slots or holes in metal members, the cable shall be pro- 
tected by listed bushings or listed grommets covering all 
metal edges that are securely fastened in the opening prior 
to installation of the cable. 

(2) Nonmetallic-Sheathed Cable and Electrical Non- 
metallic Tubing. Where nails or screws are likely to pen- 
etrate nonmetallic-sheathed cable or electrical nonmetallic 
tubing, a steel sleeve, steel plate, or steel clip not less than 
1.6 mm (V\6 in.) in thickness shall be used to protect the 
cable or tubing. 

(C) Cables Through Spaces Behind Panels Designed to 
Allow Access. Cables or raceway-type wiring methods, in- 
stalled behind panels designed to allow access, shall be 
supported according to their applicable articles. 

(D) Cables and Raceways Parallel to Framing 
Members. In both exposed and concealed locations, where 
a cable- or raceway-type wiring method is installed parallel 
to framing members, such as joists, rafters, or studs, the 
cable or raceway shall be installed and supported so that the 
nearest outside surface of the cable or raceway is not less 
than 32 mm (VA in.) from the nearest edge of the framing 
member where nails or screws are likely to penetrate. 



• 



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ARTICLE 300 — WIRING METHODS 



70-125 



Where this distance cannot be maintained, the cable or 
raceway shall be protected from penetration by nails or 
screws by a steel plate, sleeve, or equivalent at least 
1.6 mm (Vie in.) thick. 

Exception No. 1: Steel plates, sleeves, or the equivalent, 
shall not be required to protect rigid metal conduit, inter- 
mediate metal conduit, rigid nonmetallic conduit, or elec- 
trical metallic tubing. 

Exception No. 2: For concealed work in finished buildings, 
or finished panels for prefabricated buildings where such 
supporting is impracticable, it shall be permissible to fish 
the cables between access points. 

(E) Cables and Raceways Installed in Shallow Grooves. 

Cable- or raceway-type wiring methods installed in a 
groove, to be covered by wallboard, siding, paneling, car- 
peting, or similar finish, shall be protected by 1.6 mm (Vie 
in.) thick steel plate, sleeve, or equivalent or by not less 
than 32 mm (l l A in.) free space for the full length of the 
groove in which the cable or raceway is installed. 

Exception: Steel plates, sleeves, or the equivalent shall not 
be required to protect rigid metal conduit, intermediate 
metal conduit, rigid nonmetallic conduit, or electrical me- 
tallic tubing. 

(F) Insulated Fittings. Where raceways containing un- 
grounded conductors 4 AWG or larger enter a cabinet, box 
enclosure, or raceway, the conductors shall be protected by 
a substantial fitting providing a smoothly rounded insulat- 
ing surface, unless the conductors are separated from the 
fitting or raceway by substantial insulating material that is 
securely fastened in place. 

Exception: Where threaded hubs or bosses that are an in- 
tegral part of a cabinet, box enclosure, or raceway provide 
a smoothly rounded or flared entry for conductors. 

Conduit bushings constructed wholly of insulating ma- 
terial shall not be used to secure a fitting or raceway. The 
insulating fitting or insulating material shall have a tem- 
perature rating not less than the insulation temperature rat- 
ing of the installed conductors. 

300.5 Underground Installations. 

(A) Minimum Cover Requirements. Direct-buried cable 
or conduit or other raceways shall be installed to meet the 
minimum cover requirements of Table 300.5. 

(B) Grounding. All underground installations shall be 
grounded and bonded in accordance with Article 250. 

(C) Underground Cables Under Buildings. Underground 
cable installed under a building shall be in a raceway that is 
extended beyond the outside walls of the building. 



(D) Protection from Damage. Direct-buried conductors 
and cables shall be protected from damage in accordance 
with (1) through (5). 

(1) Emerging from Grade. Direct-buried conductors and 
enclosures emerging from grade shall be protected by en- 
closures or raceways extending from the minimum cover 
distance required by 300.5(A) below grade to a point at 
least 2.5 m (8 ft) above finished grade. In no case shall the 
protection be required to exceed 450 mm (18 in.) below 
finished grade. 

(2) Conductors Entering Buildings. Conductors entering 
a building shall be protected to the point of entrance. 

(3) Service Conductors. Underground service conductors 
that are not encased in concrete and that are buried 450 mm 
(18 in.) or more below grade shall have their location iden- 
tified by a warning ribbon that is placed in the trench at 
least 300 mm (12 in.) above the underground installation. 

(4) Enclosure or Raceway Damage. Where the enclosure 
or raceway is subject to physical damage, the conductors 
shall be installed in rigid metal conduit, intermediate metal 
conduit, Schedule 80 rigid nonmetallic conduit, or equiva- 
lent. 

(5) Listing. Cables and insulated conductors installed in 
enclosures or raceways in underground installations shall 
be listed for use in wet locations. 

(E) Splices and Taps. Direct-buried conductors or cables 
shall be permitted to be spliced or tapped without the use of 
splice boxes. The splices or taps shall be made in accor- 
dance with 110.14(B). 

(F) Backfill. Backfill that contains large rocks, paving ma- 
terials, cinders, large or sharply angular substances, or cor- 
rosive material shall not be placed in an excavation where 
materials may damage raceways, cables, or other substruc- 
tures or prevent adequate compaction of fill or contribute to 
corrosion of raceways, cables, or other substructures. 

Where necessary to prevent physical damage to the 
raceway or cable, protection shall be provided in the form 
of granular or selected material, suitable running boards, 
suitable sleeves, or other approved means. 

(G) Raceway Seals. Conduits or raceways through which 
moisture may contact energized live parts shall be sealed or 
plugged at either or both ends. 

FPN: Presence of hazardous gases or vapors may also ne- 
cessitate sealing of underground conduits or raceways en- 
tering buildings. 

(H) Bushing. A bushing, or terminal fitting, with an inte- 
gral bushed opening shall be used at the end of a conduit or 
other raceway that terminates underground where the con- 



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Table 300.5 Minimum Cover Requirements, to 600 Volts, Nominal, Burial in Millimeters (Inches) 





Type of Wiring Method or Circuit 












Column 5 












Circuits for 












Control of 










Column 4 


Irrigation and 








Column 3 


Residential Branch 


Landscape 








Nonmetallic 


Circuits Rated 120 


Lighting Limited 








Raceways Listed 


Volts or Less with 


to Not More Than 






Column 2 


for Direct Burial 


GFCI Protection 


30 Volts and 




Column 1 


Rigid Metal 


Without Concrete 


and Maximum 


Installed with Type 




Direct Burial 


Conduit or 


Encasement or 


Overcurrent 


UF or in Other 




Cables or 


Intermediate Metal 


Other Approved 


Protection of 20 


Identified Cable or 




Conductors 


Conduit 


Raceways 


Amperes 


Raceway 


Location of Wiring 






















Method or Circuit 


mm in. 


mm in. 


mm in. 


mm in. 


mm in. 


All locations not 


600 24 


150 6 


450 18 


300 12 


150 6 


specified below 












In trench below 50-mm 


450 18 


150 6 


300 12 


150 6 


150 6 


(2-in.) thick concrete 












or equivalent 












Under a building 



















(in raceway only) 






(in raceway only) 


(in raceway only) 


Under minimum of 


450 18 


100 4 


100 4 


150 6 


150 6 


102-mm (4-in.) thick 








(direct burial) 




concrete exterior slab 








100 4 




with no vehicular 








(in raceway) 




traffic and the slab 












extending not less than 












152 mm (6 in.) beyond 












the underground 












installation 












Under streets, highways, 


600 24 


600 24 


600 24 


600 24 


600 24 


roads, alleys, 












driveways, and parking 












lots 












One- and two-family 


450 18 


450 18 


450 18 


300 12 


450 18 


dwelling driveways 












and outdoor parking 












areas, and used only 












for dwelling-related 












purposes 












In or under airport 


450 18 


450 18 


450 18 


450 18 


450 18 


runways, including 












adjacent areas where 












trespassing prohibited 













Notes: 

1. Cover is defined as the shortest distance in millimeters (inches) 
measured between a point on the top surface of any direct-buried 
conductor, cable, conduit, or other raceway and the top surface of 
finished grade, concrete, or similar cover. 

2. Raceways approved for burial only where concrete encased shall 
require concrete envelope not less than 50 mm (2 in.) thick. 

3. Lesser depths shall be permitted where cables and conductors rise 
for terminations or splices or where access is otherwise required. 



4. Where one of the wiring method types listed in Columns 1-3 is 
used for one of the circuit types in Columns 4 and 5, the shallower 
depth of burial shall be permitted. 

5. Where solid rock prevents compliance with the cover depths speci- 
fied in this table, the wiring shall be installed in metal or nonmetallic 
raceway permitted for direct burial. The raceways shall be covered by 
a minimum of 50 mm (2 in.) of concrete extending down to rock. 



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ARTICLE 300 — WIRING METHODS 



70-127 



ductors or cables emerge as a direct burial wiring method. 
A seal incorporating the physical protection characteristics 
of a bushing shall be permitted to be used in lieu of a 
bushing. 

(I) Conductors of the Same Circuit. All conductors of 
the same circuit and, where used, the grounded conductor 
and all equipment grounding conductors shall be installed 
in the same raceway or cable or shall be installed in close 
proximity in the same trench. 

Exception No. 1: Conductors in parallel in raceways or 
cables shall be permitted, but each raceway or cable shall 
contain all conductors of the same circuit including 
grounding conductors. 

Exception No. 2: Isolated phase, polarity, grounded con- 
ductor, and equipment grounding and bonding conductor 
installations shall be permitted in nonmetallic raceways or 
cables with a nonmetallic covering or nonmagnetic sheath 
in close proximity where conductors are paralleled as per- 
mitted in 310.4, and where the conditions of 300.20(B) are 
met. 

(J) Ground Movement. Where direct-buried conductors, 
raceways, or cables are subject to movement by settlement 
or frost, direct-buried conductors, raceways, or cables shall 
be arranged to prevent damage to the enclosed conductors 
or to equipment connected to the raceways. 

FPN: This section recognizes "S" loops in underground 
direct burial to raceway transitions, expansion fittings in 
raceway risers to fixed equipment, and, generally, the pro- 
vision of flexible connections to equipment subject to 
settlement or frost heaves. 

(K) Directional Boring. Cables or raceways installed us- 
ing directional boring equipment shall be approved for the 
purpose. 

300.6 Protection Against Corrosion. Metal raceways, 
cable trays, cablebus, auxiliary gutters, cable armor, boxes, 
cable sheathing, cabinets, elbows, couplings, fittings, sup- 
ports, and support hardware shall be of materials suitable 
for the environment in which they are to be installed. 

(A) General. Ferrous raceways, cable trays, cablebus, aux- 
iliary gutters, cable armor, boxes, cable sheathing, cabinets, 
metal elbows, couplings, fittings, supports, and support 
hardware shall be suitably protected against corrosion in- 
side and outside (except threads at joints) by a coating of 
approved corrosion-resistant material such as zinc, cad- 
mium, or enamel. Where protected from corrosion solely 
by enamel, they shall not be used outdoors or in wet loca- 
tions as described in 300.6(C). Where boxes or cabinets 
have an approved system of organic coatings and are 
marked "Raintight," "Rainproof," or "Outdoor Type," they 
shall be permitted outdoors. Where corrosion protection is 



necessary and the conduit is threaded in the field, the 
threads shall be coated with an approved electrically con- 
ductive, corrosion-resistant compound. 

(B) In Concrete or in Direct Contact with the Earth. 

Ferrous or nonferrous metal raceways, cable armor, boxes, 
cable sheathing, cabinets, elbows, couplings, fittings, sup- 
ports, and support hardware shall be permitted to be in- 
stalled in concrete or in direct contact with the earth, or in 
areas subject to severe corrosive influences where made of 
material judged suitable for the condition, or where pro- 
vided with corrosion protection approved for the condition. 

(C) Indoor Wet Locations. In portions of dairy processing 
facilities, laundries, canneries, and other indoor wet loca- 
tions, and in locations where walls are frequently washed or 
where there are surfaces of absorbent materials, such as 
damp paper or wood, the entire wiring system, where in- 
stalled exposed, including all boxes, fittings, conduits, and 
cable used therewith, shall be mounted so that there is at 
least a 6-mm (Vi-in.) airspace between it and the wall or 
supporting surface. 

Exception: Nonmetallic raceways, boxes, and fittings shall 
be permitted to be installed without the airspace on a con- 
crete, masonry, tile, or similar surface. 

FPN: In general, areas where acids and alkali chemicals 
are handled and stored may present such corrosive condi- 
tions, particularly when wet or damp. Severe corrosive con- 
ditions may also be present in portions of meatpacking 
plants, tanneries, glue houses, and some stables; in instal- 
lations immediately adjacent to a seashore and swimming 
pool areas; in areas where chemical deicers are used; and in 
storage cellars or rooms for hides, casings, fertilizer, salt, 
and bulk chemicals. 

300.7 Raceways Exposed to Different Temperatures. 

(A) Sealing. Where portions of a cable, raceway, or sleeve 
are known to be subjected to different temperatures and 
where condensation is known to be a problem, as in cold 
storage areas of buildings or where passing from the inte- 
rior to the exterior of a building, the raceway or sleeve shall 
be filled with an approved material to prevent the circula- 
tion of warm air to a colder section of the raceway or 
sleeve. An explosionproof seal shall not be required for this 
purpose. 

(B) Expansion Fittings. Raceways shall be provided with 
expansion fittings where necessary to compensate for ther- 
mal expansion and contraction. 

FPN: Table 352.44(A) provides the expansion information 
for polyvinyl chloride (PVC). A nominal number for steel 
conduit can be determined by multiplying the expansion 
length in this table by 0.20. The coefficient of expansion for 
steel electrical metallic tubing, intermediate metal conduit, 
and rigid conduit is 11.70 x 10 _6 (0.0000117 mm per mm of 



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70-128 



ARTICLE 300 — WIRING METHODS 



conduit for each °C in temperature change) [6.50 x 1CT 6 
(0.0000065 in. per inch of conduit for each °F in tempera- 
ture change)]. 

300.8 Installation of Conductors with Other Systems. 

Raceways or cable trays containing electric conductors 
shall not contain any pipe, tube, or equal for steam, water, 
air, gas, drainage, or any service other than electrical. 

300.10 Electrical Continuity of Metal Raceways and 
Enclosures. Metal raceways, cable armor, and other metal 
enclosures for conductors shall be metallically joined to- 
gether into a continuous electric conductor and shall be 
connected to all boxes, fittings, and cabinets so as to pro- 
vide effective electrical continuity. Unless specifically per- 
mitted elsewhere in this Code, raceways and cable assem- 
blies shall be mechanically secured to boxes, fittings, 
cabinets, and other enclosures. 

Exception No. 1: Short sections of raceways used to pro- 
vide support or protection of cable assemblies from physi- 
cal damage shall not be required to be made electrically 
continuous. 

Exception No. 2: Equipment enclosures to be isolated, as 
permitted by 250.96(B), shall not be required to be metal- 
lically joined to the metal raceway. 

300.11 Securing and Supporting. 

(A) Secured in Place. Raceways, cable assemblies, boxes, 
cabinets, and fittings shall be securely fastened in place. 
Support wires that do not provide secure support shall not 
be permitted as the sole support. Support wires and associ- 
ated fittings that provide secure support and that are in- 
stalled in addition to the ceiling grid support wires shall be 
permitted as the sole support. Where independent support 
wires are used, they shall be secured at both ends. Cables 
and raceways shall not be supported by ceiling grids. 

(1) Fire-Rated Assemblies. Wiring located within the cav- 
ity of a fire-rated floor-ceiling or roof-ceiling assembly 
shall not be secured to, or supported by, the ceiling assem- 
bly, including the ceiling support wires. An independent 
means of secure support shall be provided. Where indepen- 
dent support wires are used, they shall be distinguishable 
by color, tagging, or other effective means from those that 
are part of the fire-rated design. 

Exception: The ceiling support system shall be permitted 
to support wiring and equipment that have been tested as 
part of the fire-rated assembly. 

FPN: One method of determining fire rating is testing in 
accordance with NFPA 251-1999, Standard Methods of 
Tests of Fire Endurance of Building Construction and 
Materials. 



(2) Non-Fire-Rated Assemblies. Wiring located within 
the cavity of a non-fire-rated floor-ceiling or roof-ceiling 
assembly shall not be secured to, or supported by, the ceil- 
ing assembly, including the ceiling support wires. An inde- 
pendent means of secure support shall be provided. 

Exception: The ceiling support system shall be permitted 
to support branch-circuit wiring and associated equipment 
where installed in accordance with the ceiling system 
manufacturer 's instructions. 

(B) Raceways Used as Means of Support. Raceways 
shall only be used as a means of support for other race- 
ways, cables, or nonelectric equipment under the following 
conditions: 

(1) Where the raceway or means of support is identified for 
the purpose; or 

(2) Where the raceway contains power supply conductors 
for electrically controlled equipment and is used to sup- 
port Class 2 circuit conductors or cables that are solely 
for the purpose of connection to the equipment control 
circuits; or 

(3) Where the raceway is used to support boxes or conduit 
bodies in accordance with 314.23 or to support lumi- 
naires (fixtures) in accordance with 410.16(F) 

(C) Cables Not Used as Means of Support. Cable wiring 
methods shall not be used as a means of support for other 
cables, raceways, or nonelectrical equipment. 

300.12 Mechanical Continuity — Raceways and 
Cables. Metal or nonmetallic raceways, cable armors, and 
cable sheaths shall be continuous between cabinets, boxes, 
fittings, or other enclosures or outlets. 

Exception: Short sections of raceways used to provide sup- 
port or protection of cable assemblies from physical dam- 
age shall not be required to be mechanically continuous. 



300.13 Mechanical and Electrical Continuity 
ductors. 



Con- 



(A) General. Conductors in raceways shall be continuous 
between outlets, boxes, devices, and so forth. There shall be 
no splice or tap within a raceway unless permitted by 
300.15; 368.8(A); 376.56; 378.56; 384.56; 386.56; 388.56; 
or 390.6. 

(B) Device Removal. In multiwire branch circuits, the 
continuity of a grounded conductor shall not depend on 
device connections such as lampholders, receptacles, and 
so forth, where the removal of such devices would interrupt 
the continuity. 

300.14 Length of Free Conductors at Outlets, Junc- 
tions, and Switch Points. At least 150 mm (6 in.) of free 



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ARTICLE 300 — WIRING METHODS 



70-129 



conductor, measured from the point in the box where it 
emerges from its raceway or cable sheath, shall be left at 
each outlet, junction, and switch point for splices or the 
connection of luminaires (fixtures) or devices. Where the 
opening to an outlet, junction, or switch point is less than 
200 mm (8 in.) in any dimension, each conductor shall be 
long enough to extend at least 75 mm (3 in.) outside the 
opening. 

Exception: Conductors that are not spliced or terminated 
at the outlet, junction, or switch point shall not be required 
to comply with 300.14. 

300.15 Boxes, Conduit Bodies, or Fittings — Where 
Required. A box shall be installed at each outlet and 
switch point for concealed knob-and-tube wiring. 

Fittings and connectors shall be used only with the spe- 
cific wiring methods for which they are designed and listed. 

Where the wiring method is conduit, tubing, Type AC 
cable, Type MC cable, Type MI cable, nonmetallic- 
sheathed cable, or other cables, a box or conduit body com- 
plying with Article 314 shall be installed at each conductor 
splice point, outlet point, switch point, junction point, ter- 
mination point, or pull point, unless otherwise permitted in 
300.15(A) through (M). 

(A) Wiring Methods with Interior Access. A box or con- 
duit body shall not be required for each splice, junction, 
switch, pull, termination, or outlet points in wiring methods 
with removable covers, such as wireways, multioutlet as- 
semblies, auxiliary gutters, and surface raceways. The cov- 
ers shall be accessible after installation. 

(B) Equipment. An integral junction box or wiring com- 
partment as part of approved equipment shall be permitted 
in lieu of a box. 

(C) Protection. A box or conduit body shall not be re- 
quired where cables enter or exit from conduit or tubing 
that is used to provide cable support or protection against 
physical damage. A fitting shall be provided on the end(s) 
of the conduit or tubing to protect the cable from abrasion. 

(D) Type MI Cable. A box or conduit body shall not be 
required where accessible fittings are used for straight- 
through splices in mineral-insulated metal-sheathed cable. 

(E) Integral Enclosure. A wiring device with integral en- 
closure identified for the use, having brackets that securely 
fasten the device to walls or ceilings of conventional on- 
site frame construction, for use with nonmetallic-sheathed 
cable, shall be permitted in lieu of a box or conduit body. 

FPN: See 334.30(C); 545.10; 550.15(1); 551.47(E), Excep- 
tion No. 1; and 552.48(E), Exception No. 1. 

(F) Fitting. A fitting identified for the use shall be permit- 
ted in lieu of a box or conduit body where conductors are 



not spliced or terminated within the fitting. The fitting shall 
be accessible after installation. 

(G) Direct-Buried Conductors. As permitted in 300.5(E), 
a box or conduit body shall not be required for splices and 
taps in direct-buried conductors and cables. 

(H) Insulated Devices. As permitted in 334.40(B), a box 
or conduit body shall not be required for insulated devices 
supplied by nonmetallic-sheathed cable. 

(I) Enclosures. A box or conduit body shall not be re- 
quired where a splice, switch, terminal, or pull point is in a 
cabinet or cutout box, in an enclosure for a switch or over- 
current device as permitted in 312.8, in a motor controller 
as permitted in 430.10(A), or in a motor control center. 

(J) Luminaires (Fixtures). A box or conduit body shall 
not be required where a luminaire (fixture) is used as a 
raceway as permitted in 410.31 and 410.32. 

(K) Embedded. A box or conduit body shall not be re- 
quired for splices where conductors are embedded as per- 
mitted in 424.40, 424.41(D), 426.22(B), 426.24(A), and 
427.19(A). 

(L) Manholes. Where accessible only to qualified persons, 
a box or conduit body shall not be required for conductors 
in manholes, except where connecting to electrical equip- 
ment. The installation shall comply with the provisions of 
Part IV of Article 314. 

(M) Closed Loop. A box shall not be required with a 
closed-loop power distribution system where a device iden- 
tified and listed as suitable for installation without a box is 
used. 

300.16 Raceway or Cable to Open or Concealed Wiring. 

(A) Box or Fitting. A box or terminal fitting having a 
separately bushed hole for each conductor shall be used 
wherever a change is made from conduit, electrical metallic 
tubing, electrical nonmetallic tubing, nonmetallic-sheathed 
cable, Type AC cable, Type MC cable, or mineral-insulated, 
metal-sheathed cable and surface raceway wiring to open 
wiring or to concealed knob-and-tube wiring. A fitting used 
for this purpose shall contain no taps or splices and shall 
not be used at luminaire (fixture) outlets. 

(B) Bushing. A bushing shall be permitted in lieu of a box 
or terminal where the conductors emerge from a raceway 
and enter or terminate at equipment, such as open switch- 
boards, unenclosed control equipment, or similar equip- 
ment. The bushing shall be of the insulating type for other 
than lead-sheathed conductors. 



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ARTICLE 300 — WIRING METHODS 



300.17 Number and Size of Conductors in Raceway. 

The number and size of conductors in any raceway shall 
not be more than will permit dissipation of the heat and 
ready installation or withdrawal of the conductors without 
damage to the conductors or to their insulation. 

FPN: See the following sections of this Code: intermediate 
metal conduit, 342.22; rigid metal conduit, 344.22; flexible 
metal conduit, 348.22; liquidtight flexible metal conduit, 
350.22; rigid nonmetallic conduit, 352.22; liquidtight non- 
metallic flexible conduit, 356.22; electrical metallic tubing, 
358.22; flexible metallic tubing, 360.22; electrical nonme- 
tallic tubing, 362.22; cellular concrete floor raceways, 
372.11; cellular metal floor raceways, 374.5; metal wire- 
ways, 376.22; nonmetallic wireways, 378.22; surface metal 
raceways, 386.22; surface nonmetallic raceways 388.22; 
underfloor raceways, 390.5; fixture wire, 402.7; theaters, 
520.6; signs, 600.31(C); elevators, 620.33; audio signal 
processing, amplification, and reproduction equipment, 
640.23(A) and 640.24; Class 1, Class 2, and Class 3 cir- 
cuits, Article 725; fire alarm circuits, Article 760; and opti- 
cal fiber cables and raceways, Article 770. 

300.18 Raceway Installations. 

(A) Complete Runs. Raceways, other than busways or ex- 
posed raceways having hinged or removable covers, shall 
be installed complete between outlet, junction, or splicing 
points prior to the installation of conductors. Where re- 
quired to facilitate the installation of utilization equipment, 
the raceway shall be permitted to be initially installed with- 
out a terminating connection at the equipment. Prewired 
raceway assemblies shall be permitted only where specifi- 
cally permitted in this Code for the applicable wiring 
method. 

(B) Welding. Metal raceways shall not be supported, ter- 
minated, or connected by welding to the raceway unless 
specifically designed to be or otherwise specifically permit- 
ted to be in this Code. 

300.19 Supporting Conductors in Vertical Raceways. 

(A) Spacing Intervals — Maximum. Conductors in ver- 
tical raceways shall be supported if the vertical rise exceeds 

Table 300.19(A) Spacings for Conductor Supports 



the values in Table 300.19(A). One cable support shall be 
provided at the top of the vertical raceway or as close to the 
top as practical. Intermediate supports shall be provided as 
necessary to limit supported conductor lengths to not 
greater than those values specified in Table 300.19(A). 

Exception: Steel wire armor cable shall be supported at 
the top of the riser with a cable support that clamps the 
steel wire armor. A safety device shall be permitted at the 
lower end of the riser to hold the cable in the event there is 
slippage of the cable in the wire-armored cable support. 
Additional wedge-type supports shall be permitted to re- 
lieve the strain on the equipment terminals caused by ex- 
pansion of the cable under load. 

(B) Support Methods. One of the following methods of 
support shall be used. 

(1) By clamping devices constructed of or employing insu- 
lating wedges inserted in the ends of the raceways. 
Where clamping of insulation does not adequately sup- 
port the cable, the conductor also shall be clamped. 

(2) By inserting boxes at the required intervals in which 
insulating supports are installed and secured in a satis- 
factory manner to withstand the weight of the conduc- 
tors attached thereto, the boxes being provided with 
covers. 

(3) In junction boxes, by deflecting the cables not less than 
90 degrees and carrying them horizontally to a distance 
not less than twice the diameter of the cable, the cables 
being carried on two or more insulating supports and 
additionally secured thereto by tie wires if desired. 
Where this method is used, cables shall be supported at 
intervals not greater than 20 percent of those mentioned 
in the preceding tabulation. 

(4) By a method of equal effectiveness. 

300.20 Induced Currents in Metal Enclosures or Metal 
Raceways. 

(A) Conductors Grouped Together. Where conductors 
carrying alternating current are installed in metal enclo- 



Size of Wire 



Conductors 



Support of Conductors in 
Vertical Raceways 



Aluminum or Copper-Clad 
Aluminum 

m ft 



Copper 



m 



ft 



18 AWG through 8 AWG Not greater than 

6 AWG through 1/0 AWG Not greater than 

2/0 AWG through 4/0 AWG Not greater than 

Over 4/0 AWG through 350 kcmil Not greater than 

Over 350 kcmil through 500 kcmil Not greater than 

Over 500 kcmil through 750 kcmil Not greater than 

Over 750 kcmil Not greater than 



30 
60 
55 
41 
36 
28 
26 



100 
200 
180 
135 
120 
95 
85 



30 
30 
25 
18 
15 
12 
11 



100 
100 
80 
60 
50 
40 
35 



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ARTICLE 300 — WIRING METHODS 



70-131 



sures or metal raceways, they shall be arranged so as to 
avoid heating the surrounding metal by induction. To ac- 
complish this, all phase conductors and, where used, the 
grounded conductor and all equipment grounding conduc- 
tors shall be grouped together. 

Exception No. 1: Equipment grounding conductors for cer- 
tain existing installations shall be permitted to be installed 
separate from their associated circuit conductors where run 
in accordance with the provisions of 250.130(C). 

Exception No. 2: A single conductor shall be permitted to 
be installed in a ferromagnetic enclosure and used for skin- 
effect heating in accordance with the provisions of 426.42 
and 427.47. 

(B) Individual Conductors. Where a single conductor 
carrying alternating current passes through metal with mag- 
netic properties, the inductive effect shall be minimized by 
(1) cutting slots in the metal between the individual holes 
through which the individual conductors pass or (2) passing 
all the conductors in the circuit through an insulating wall 
sufficiently large for all of the conductors of the circuit. 

Exception: In the case of circuits supplying vacuum or 
electric-discharge lighting systems or signs or X-ray appa- 
ratus, the currents carried by the conductors are so small 
that the inductive heating effect can be ignored where these 
conductors are placed in metal enclosures or pass through 
metal. 

FPN: Because aluminum is not a magnetic metal, there 
will be no heating due to hysteresis; however, induced cur- 
rents will be present. They will not be of sufficient magni- 
tude to require grouping of conductors or special treatment 
in passing conductors through aluminum wall sections. 

300.21 Spread of Fire or Products of Combustion. 

Electrical installations in hollow spaces, vertical shafts, and 
ventilation or air-handling ducts shall be made so that the 
possible spread of fire or products of combustion will not 
be substantially increased. Openings around electrical pen- 
etrations through fire-resistant-rated walls, partitions, 
floors, or ceilings shall be firestopped using approved meth- 
ods to maintain the fire resistance rating. 

FPN: Directories of electrical construction materials pub- 
lished by qualified testing laboratories contain many listing 
installation restrictions necessary to maintain the fire- 
resistive rating of assemblies where penetrations or open- 
ings are made. Building codes also contain restrictions on 
membrane penetrations on opposite sides of a fire- 
resistance-rated wall assembly. An example is the 600-mm 
(24-in.) minimum horizontal separation that usually applies 
between boxes installed on opposite sides of the wall. As- 
sistance in complying with 300.21 can be found in building 
codes, fire resistance directories, and product listings. 

300.22 Wiring in Ducts, Plenums, and Other Air- 
Handling Spaces. The provisions of this section apply to 



the installation and uses of electric wiring and equipment in 
ducts, plenums, and other air-handling spaces. 

FPN: See Article 424, Part VI, for duct heaters. 

(A) Ducts for Dust, Loose Stock, or Vapor Removal. No 

wiring systems of any type shall be installed in ducts used 
to transport dust, loose stock, or flammable vapors. No 
wiring system of any type shall be installed in any duct, or 
shaft containing only such ducts, used for vapor removal or 
for ventilation of commercial-type cooking equipment. 

(B) Ducts or Plenums Used for Environmental Air. Only 
wiring methods consisting of Type MI cable, Type MC 
cable employing a smooth or corrugated impervious metal 
sheath without an overall nonmetallic covering, electrical 
metallic tubing, flexible metallic tubing, intermediate metal 
conduit, or rigid metal conduit without an overall nonme- 
tallic covering shall be installed in ducts or plenums spe- 
cifically fabricated to transport environmental air. Flexible 
metal conduit and liquidtight flexible metal conduit shall be 
permitted, in lengths not to exceed 1.2 m (4 ft), to connect 
physically adjustable equipment and devices permitted to 
be in these ducts and plenum chambers. The connectors 
used with flexible metal conduit shall effectively close any 
openings in the connection. Equipment and devices shall be 
permitted within such ducts or plenum chambers only if 
necessary for their direct action upon, or sensing of, the 
contained air. Where equipment or devices are installed and 
illumination is necessary to facilitate maintenance and re- 
pair, enclosed gasketed-type luminaires (fixtures) shall be 
permitted. 

(C) Other Space Used for Environmental Air. This sec- 
tion applies to space used for environmental air-handling 
purposes other than ducts and plenums as specified in 
300.22(A) and (B). It does not include habitable rooms or 
areas of buildings, the prime purpose of which is not air 
handling. 

FPN: The space over a hung ceiling used for environmen- 
tal air-handling purposes is an example of the type of other 
space to which this section applies. 

Exception: This section shall not apply to the joist or stud 
spaces of dwelling units where the wiring passes through 
such spaces perpendicular to the long dimension of such 
spaces. 

(1) Wiring Methods. The wiring methods for such other 
space shall be limited to totally enclosed, nonventilated, 
insulated bus way having no provisions for plug-in connec- 
tions, Type MI cable, Type MC cable without an overall 
nonmetallic covering, Type AC cable, or other factory- 
assembled multiconductor control or power cable that is 
specifically listed for the use, or listed prefabricated cable 
assemblies of metallic manufactured wiring systems with- 



NATIONAL ELECTRICAL CODE 



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ARTICLE 300 — WIRING METHODS 



out nonmetallic sheath. Other types of cables and conduc- 
tors shall be installed in electrical metallic tubing, flexible 
metallic tubing, intermediate metal conduit, rigid metal 
conduit without an overall nonmetallic covering, flexible 
metal conduit, or, where accessible, surface metal raceway 
or metal wireway with metal covers or solid bottom metal 
cable tray with solid metal covers. 

(2) Equipment. Electrical equipment with a metal enclo- 
sure, or with a nonmetallic enclosure listed for the use and 
having adequate fire-resistant and low-smoke-producing 
characteristics, and associated wiring material suitable for 
the ambient temperature shall be permitted to be installed 
in such other space unless prohibited elsewhere in this 
Code. 

Exception: Integral fan systems shall be permitted where 
specifically identified for such use. 

(D) Information Technology Equipment. Electric wiring 
in air-handling areas beneath raised floors for information 
technology equipment shall be permitted in accordance 
with Article 645. 

300.23 Panels Designed to Allow Access. Cables, race- 
ways, and equipment installed behind panels designed to 
allow access, including suspended ceiling panels, shall be 
arranged and secured so as to allow the removal of panels 
and access to the equipment. 

II. Requirements for Over 600 Volts, Nominal 

300.31 Covers Required. Suitable covers shall be in- 
stalled on all boxes, fittings, and similar enclosures to pre- 
vent accidental contact with energized parts or physical 
damage to parts or insulation. 



termediate metal conduit, in electrical metallic tubing, in 
rigid nonmetallic conduit, in cable trays, as busways, as 
cablebus, in other identified raceways, or as open runs of 
metal-clad cable suitable for the use and purpose. In loca- 
tions accessible to qualified persons only, open runs of 
Type MV cables, bare conductors, and bare busbars shall 
also be permitted. Busbars shall be permitted to be either 
copper or aluminum. 

300.39 Braid-Covered Insulated Conductors — Open 
Installation. Open runs of braid-covered insulated conduc- 
tors shall have a fiame-retardant braid. If the conductors 
used do not have this protection, a fiame-retardant saturant 
shall be applied to the braid covering after installation. This 
treated braid covering shall be stripped back a safe distance 
at conductor terminals, according to the operating voltage. 
This distance shall not be less than 25 mm (1 in.) for each 
kilovolt of the conductor-to-ground voltage of the circuit, 
where practicable. 

300.40 Insulation Shielding. Metallic and semiconducting 
insulation shielding components of shielded cables shall be 
removed for a distance dependent on the circuit voltage and 
insulation. Stress reduction means shall be provided at all 
terminations of factory-applied shielding. 

Metallic shielding components such as tapes, wires, or 
braids, or combinations thereof, and their associated con- 
ducting or semiconducting components shall be grounded. 

300.42 Moisture or Mechanical Protection for Metal- 
Sheathed Cables. Where cable conductors emerge from a 
metal sheath and where protection against moisture or 
physical damage is necessary, the insulation of the conduc- 
tors shall be protected by a cable sheath terminating device. 



300.32 Conductors of Different Systems. See 300.3(C)(2). 300.50 Underground Installations. 



300.34 Conductor Bending Radius. The conductor shall 
not be bent to a radius less than 8 times the overall diameter 
for nonshielded conductors or 12 times the diameter for 
shielded or lead-covered conductors during or after instal- 
lation. For multiconductor or multiplexed single conductor 
cables having individually shielded conductors, the mini- 
mum bending radius is 12 times the diameter of the indi- 
vidually shielded conductors or 7 times the overall diam- 
eter, whichever is greater. 

300.35 Protection Against Induction Heating. Metallic 
raceways and associated conductors shall be arranged so as 
to avoid heating of the raceway in accordance with the 
applicable provisions of 300.20. 

300.37 Aboveground Wiring Methods. Aboveground 
conductors shall be installed in rigid metal conduit, in in- 



(A) General. Underground conductors shall be identified 
for the voltage and conditions under which they are in- 
stalled. Direct burial cables shall comply with the provi- 
sions of 310.7. Underground cables shall be installed in 
accordance with 300.50(A)(1) or (2), and the installation 
shall meet the depth requirements of Table 300.50. 

Exception No. 1: Areas subject to vehicular traffic, such as 
thoroughfares or commercial parking areas, shall have a 
minimum cover of 600 mm (24 in.). 

Exception No. 2: The minimum cover requirements for 
other than rigid metal conduit and intermediate metal con- 
duit shall be permitted to be reduced 150 mm (6 in.) for 
each 50 mm (2 in.) of concrete or equivalent protection 
placed in the trench over the underground installation. 

Exception No. 3: The minimum cover requirements shall 
not apply to conduits or other raceways that are located 



2002 Edition 



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ARTICLE 310 — CONDUCTORS FOR GENERAL WRING 



70-133 



Table 300.50 Minimum Cover Requirements 









Rigid 


Rigid Metal 








Nonmetallic 


Conduit 








Conduit 


and 




Direct- 


Approved 


Intermediate 




Buried 


for Direct 


Metal 




Cables 


Burial* 


Conduit 


Circuit 


















Voltage 


mm 


in. 


mm in. 


mm in. 


Over 600 V 


750 


30 


450 18 


150 6 


through 










22 kV 










Over 22 kV 


900 


36 


600 24 


150 6 


through 










40 kV 










Over 40 kV 


1000 


42 


750 30 


150 6 



Note: Cover is defined as the shortest distance in millimeters mea- 
sured between a point on the top surface of any direct-buried conduc- 
tor, cable, conduit, or other raceway and the top surface of finished 
grade, concrete, or similar cover. 

*Listed by a qualified testing agency as suitable for direct burial 
without encasement. All other nonmetallic systems shall require 
50 mm (2 in.) of concrete or equivalent above conduit in addition to 
above depth. 



under a building or exterior concrete slab not less than 
100 mm (4 in.) in thickness and extending not less than 
150 mm (6 in.) beyond the underground installation. A 
warning ribbon or other effective means suitable for the 
conditions shall be placed above the underground 
installation. 

Exception No. 4: Lesser depths shall be permitted where 
cables and conductors rise for terminations or splices or 
where access is otherwise required. 

Exception No. 5: In airport runways, including adjacent 
defined areas where trespass is prohibited, cable shall be 
permitted to be buried not less than 450 mm (18 in.) deep 
and without raceways, concrete enclosement, or equivalent. 

Exception No. 6: Raceways installed in solid rock shall be 
permitted to be buried at lesser depth where covered by 
50 mm (2 in.) of concrete, which shall be permitted to 
extend to the rock surface. 

(1) Shielded Cables and Nonshielded Cables in Metal- 
Sheathed Cable Assemblies. Underground cables, includ- 
ing nonshielded, Type MC and moisture-impervious metal 
sheath cables, shall have those sheaths grounded through an 
effective grounding path meeting the requirements of 
250.4(A)(5) or 250.4(B)(4). They shall be direct buried or 
installed in raceways identified for the use. 

(2) Other Nonshielded Cables. Other nonshielded cables 
not covered in 300.50(A)(1) shall be installed in rigid metal 
conduit, intermediate metal conduit, or rigid nonmetallic 
conduit encased in not less than 75 mm (3 in.) of concrete. 



(B) Protection from Damage. Conductors emerging from 
the ground shall be enclosed in listed raceways. Raceways 
installed on poles shall be of rigid metal conduit, interme- 
diate metal conduit, PVC Schedule 80, or equivalent, ex- 
tending from the minimum cover depth specified in Table 
300.50 to a point 2.5 m (8 ft) above finished grade. Con- 
ductors entering a building shall be protected by an ap- 
proved enclosure or raceway from the minimum cover 
depth to the point of entrance. Where direct-buried conduc- 
tors, raceways, or cables are subject to movement by settle- 
ment or frost, they shall be installed to prevent damage to 
the enclosed conductors or to the equipment connected to 
the raceways. Metallic enclosures shall be grounded. 

(C) Splices. Direct burial cables shall be permitted to be 
spliced or tapped without the use of splice boxes, provided 
they are installed using materials suitable for the applica- 
tion. The taps and splices shall be watertight and protected 
from mechanical damage. Where cables are shielded, the 
shielding shall be continuous across the splice or tap. 

Exception: At splices of an engineered cabling system, me- 
tallic shields of direct-buried single-conductor cables with 
maintained spacing between phases shall be permitted to 
be interrupted and overlapped. Where shields are inter- 
rupted and overlapped, each shield section shall be 
grounded at one point. 

(D) Backfill. Backfill containing large rocks, paving mate- 
rials, cinders, large or sharply angular substances, or corro- 
sive materials shall not be placed in an excavation where 
materials can damage raceways, cables, or other substruc- 
tures, or prevent adequate compaction of fill, or contribute 
to corrosion of raceways, cables, or other substructures. 

Protection in the form of granular or selected material 
or suitable sleeves shall be provided to prevent physical 
damage to the raceway or cable. 

(E) Raceway Seal. Where a raceway enters from an un- 
derground system, the end within the building shall be 
sealed with an identified compound so as to prevent the 
entrance of moisture or gases, or it shall be so arranged to 
prevent moisture from contacting live parts. 



ARTICLE 310 
Conductors for General Wiring 

310.1 Scope. This article covers general requirements for 
conductors and their type designations, insulations, mark- 
ings, mechanical strengths, ampacity ratings, and uses. 
These requirements do not apply to conductors that form an 
integral part of equipment, such as motors, motor control- 



NATIONAL ELECTRICAL CODE 



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ARTICLE 310 — CONDUCTORS FOR GENERAL WIRING 



lers, and similar equipment, or to conductors specifically 
provided for elsewhere in this Code. 

FPN: For flexible cords and cables, see Article 400. For 
fixture wires, see Article 402. 

310.2 Conductors. 

(A) Insulated. Conductors shall be insulated. 

Exception: Where covered or bare conductors are specifi- 
cally permitted elsewhere in this Code. 

FPN: See 250.184 for insulation of neutral conductors of a 
solidly grounded high-voltage system. 

(B) Conductor Material. Conductors in this article shall 
be of aluminum, copper-clad aluminum, or copper unless 
otherwise specified. 

310.3 Stranded Conductors. Where installed in raceways, 
conductors of size 8 AWG and larger shall be stranded. 

Exception: As permitted or required elsewhere in this 
Code. 

310.4 Conductors in Parallel. Aluminum, copper-clad 
aluminum, or copper conductors of size 1/0 AWG and 
larger, comprising each phase, neutral, or grounded circuit 
conductor, shall be permitted to be connected in parallel 
(electrically joined at both ends to form a single conductor). 

Exception No. 1: As permitted in 620.12(A)(1) . 

Exception No. 2: Conductors in sizes smaller than 1/0 
AWG shall be permitted to be run in parallel to supply 
control power to indicating instruments, contactors, relays, 
solenoids, and similar control devices provided 

(a) They are contained within the same raceway or cable, 

(b) The ampacity of each individual conductor is sufficient 
to carry the entire load current shared by the parallel 
conductors, and 

(c) The overcurrent protection is such that the ampacity of 
each individual conductor will not be exceeded if one 
or more of the parallel conductors become inadvert- 
ently disconnected. 

Exception No. 3: Conductors in sizes smaller than 1/0 
AWG shall be permitted to be run in parallel for frequen- 
cies of 360 Hz and higher where conditions (a), (b), and (c) 
of Exception No. 2 are met. 

Exception No. 4: Under engineering supervision, grounded 
neutral conductors in sizes 2 AWG and larger shall be 
permitted to be run in parallel for existing installations. 

FPN: Exception No. 4 can be used to alleviate overheating 
of neutral conductors in existing installations due to high 
content of triplen harmonic currents. 



The paralleled conductors in each phase, neutral, or 
grounded circuit conductor shall 

(1) Be the same length 

(2) Have the same conductor material 

(3) Be the same size in circular mil area 

(4) Have the same insulation type 

(5) Be terminated in the same manner 

Where run in separate raceways or cables, the raceways 
or cables shall have the same physical characteristics. Con- 
ductors of one phase, neutral, or grounded circuit conductor 
shall not be required to have the same physical character- 
istics as those of another phase, neutral, or grounded circuit 
conductor to achieve balance. 

FPN: Differences in inductive reactance and unequal divi- 
sion of current can be minimized by choice of materials, 
methods of construction, and orientation of conductors. 

Where equipment grounding conductors are used with 
conductors in parallel, they shall comply with the require- 
ments of this section except that they shall be sized in 
accordance with 250.122. 

Conductors installed in parallel shall comply with the 
provisions of 310.15(B)(2)(a). 

310.5 Minimum Size of Conductors. The minimum size 
of conductors shall be as shown in Table 310.5. 

Table 310.5 Minimum Size of Conductors 



Conductor 
Voltage Rating 

(Volts) 



Minimum Conductor Size (AWG) 



Copper 



Aluminum or Copper-Clad 
Aluminum 



0-2000 
2001-8000 
8001-15,000 
15,001-28,000 
28,001-35,000 



14 
8 
2 
1 

1/0 



12 

8 

2 

1 

1/0 



Exception No. 1: For flexible cords as permitted by 400.12. 

Exception No. 2: For fixture wire as permitted by 402.6. 

Exception No. 3: For motors rated 1 hp or less as permit- 
ted by 430.22(F). 

Exception No. 4: For cranes and hoists as permitted by 
610.14. 

Exception No. 5: For elevator control and signaling cir- 
cuits as permitted by 620.12. 

Exception No. 6: For Class 1, Class 2, and Class 3 circuits 
as permitted by 725.27(A) and 725.51, Exception. 



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ARTICLE 310 — CONDUCTORS FOR GENERAL WIRING 



70-135 



Exception No. 7: For fire alarm circuits as permitted by 
760.27(A), 760.51, Exception, and 760.71(B). 

Exception No. 8: For motor-control circuits as permitted 
by 430.72. 

Exception No. 9: For control and instrumentation circuits 
as permitted by 727.6. 

Exception No. 10: For electric signs and outline lighting 
as permitted in 600.31(B) and 600.32(B). 

310.6 Shielding. Solid dielectric insulated conductors op- 
erated above 2000 volts in permanent installations shall 
have ozone-resistant insulation and shall be shielded. All 
metallic insulation shields shall be grounded through an 
effective grounding path meeting the requirements of 
250.4(A)(5) or 250.4(B)(4). Shielding shall be for the pur- 
pose of confining the voltage stresses to the insulation. 

Exception: Nonshielded insulated conductors listed by a 
qualified testing laboratory shall be permitted for use up to 
8000 volts under the following conditions: 

(a) Conductors shall have insulation resistant to electric 
discharge and surface tracking, or the insulated con- 
ductors) shall be covered with a material resistant to 
ozone, electric discharge, and surface tracking. 

(b) Where used in wet locations, the insulated conductor(s) 
shall have an overall nonmetallic jacket or a continu- 
ous metallic sheath. 

(c) Where operated at 5001 to 8000 volts, the insulated 
conductor(s) shall have a nonmetallic jacket over the 
insulation. The insulation shall have a specific induc- 
tive capacity not greater than 3.6, and the jacket shall 
have a specific inductive capacity not greater than 10 
and not less than 6. 

(d) Insulation and jacket thicknesses shall be in accor- 
dance with Table 310.63. 

310.7 Direct Burial Conductors. Conductors used for di- 
rect burial applications shall be of a type identified for such 
use. 

Cables rated above 2000 volts shall be shielded. 

Exception: Nonshielded multiconductor cables rated 
2001-5000 volts shall be permitted if the cable has an 
overall metallic sheath or armor. 

The metallic shield, sheath, or armor shall be grounded 
through an effective grounding path meeting the require- 
ments of 250.4(A)(5) or 250.4(B)(4). 

FPN No. 1: See 300.5 for installation requirements for 
conductors rated 600 volts or less. 

FPN No. 2: See 300.50 for installation requirements for 
conductors rated over 600 volts. 



310.8 Locations. 

(A) Dry Locations. Insulated conductors and cables used 
in dry locations shall be any of the types identified in this 
Code. 

(B) Dry and Damp Locations. Insulated conductors and 
cables used in dry and damp locations shall be Types FEP, 
FEPB, MTW, PFA, RHH, RHW, RHW-2, SA, THHN, 
THW, THW-2, THHW, THHW-2, THWN, THWN-2, TW, 
XHH, XHHW, XHHW-2, Z, or ZW. 

(C) Wet Locations. Insulated conductors and cables used 
in wet locations shall be 

(1) Moisture-impervious metal-sheathed; 

(2) Types MTW, RHW, RHW-2, TW, THW, THW-2, 
THHW, THHW-2, THWN, THWN-2, XHHW, 
XHHW-2, ZW; or 

(3) Of a type listed for use in wet locations. 

(D) Locations Exposed to Direct Sunlight. Insulated con- 
ductors and cables used where exposed to direct rays of the 
sun shall be of a type listed for sunlight resistance or listed 
and marked "sunlight resistant." 

310.9 Corrosive Conditions. Conductors exposed to oils, 
greases, vapors, gases, fumes, liquids, or other substances 
having a deleterious effect on the conductor or insulation 
shall be of a type suitable for the application. 

310.10 Temperature Limitation of Conductors. No con- 
ductor shall be used in such a manner that its operating 
temperature exceeds that designated for the type of insu- 
lated conductor involved. In no case shall conductors be 
associated together in such a way with respect to type of 
circuit, the wiring method employed, or the number of con- 
ductors that the limiting temperature of any conductor is 
exceeded. 

FPN: The temperature rating of a conductor (see Table 
310.13 and Table 310.61) is the maximum temperature, at 
any location along its length, that the conductor can with- 
stand over a prolonged time period without serious degra- 
dation. The allowable ampacity tables, the ampacity tables 
of Article 310 and the ampacity tables of Annex B, the 
correction factors at the bottom of these tables, and the 
notes to the tables provide guidance for coordinating con- 
ductor sizes, types, allowable ampacities, ampacities, ambi- 
ent temperatures, and number of associated conductors. 

The principal determinants of operating temperature 
are as follows: 

(1) Ambient temperature — ambient temperature may vary 
along the conductor length as well as from time to 
time. 

(2) Heat generated internally in the conductor as the result 
of load current flow, including fundamental and har- 
monic currents. 



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ARTICLE 310 — CONDUCTORS FOR GENERAL WIRING 



(3) The rate at which generated heat dissipates into the 
ambient medium. Thermal insulation that covers or sur- 
rounds conductors affects the rate of heat dissipation. 

(4) Adjacent load-carrying conductors — adjacent conduc- 
tors have the dual effect of raising the ambient tempera- 
ture and impeding heat dissipation. 

310.11 Marking. 

(A) Required Information. All conductors and cables 
shall be marked to indicate the following information, us- 
ing the applicable method described in 310.11(B): 

(1) The maximum rated voltage. 

(2) The proper type letter or letters for the type of wire or 
cable as specified elsewhere in this Code. 

(3) The manufacturer's name, trademark, or other distinc- 
tive marking by which the organization responsible for 
the product can be readily identified. 

(4) The AWG size or circular mil area. 

FPN: See Conductor Properties, Table 8 of Chapter 9 for 
conductor area expressed in SI units for conductor sizes 
specified in AWG or circular mil area. 

(5) Cable assemblies where the neutral conductor is 
smaller than the ungrounded conductors shall be so 
marked. 

(B) Method of Marking. 

(1) Surface Marking. The following conductors and 
cables shall be durably marked on the surface. The AWG 
size or circular mil area shall be repeated at intervals not 
exceeding 610 mm (24 in.). All other markings shall be 
repeated at intervals not exceeding 1.0 m (40 in.). 

(1) Single- and multiconductor rubber- and thermoplastic- 
insulated wire and cable 

(2) Nonmetallic-sheathed cable 

(3) Service-entrance cable 

(4) Underground feeder and branch-circuit cable 

(5) Tray cable 

(6) Irrigation cable 

(7) Power-limited tray cable 

(8) Instrumentation tray cable 

(2) Marker Tape. Metal-covered multiconductor cables 
shall employ a marker tape located within the cable and 
running for its complete length. 

Exception No. 1: Mineral-insulated, metal-sheathed cable. 

Exception No. 2: Type AC cable. 

Exception No. 3: The information required in 310.11(A) 
shall be permitted to be durably marked on the outer non- 
metallic covering of Type MC, Type ITC, or Type PLTC 
cables at intervals not exceeding 1.0 m (40 in.). 

Exception No. 4: The information required in 310.11(A) 
shall be permitted to be durably marked on a nonmetallic 



covering under the metallic sheath of Type ITC or Type 
PLTC cable at intervals not exceeding 1.0 m (40 in.). 

FPN: Included in the group of metal-covered cables are 
Type AC cable (Article 320), Type MC cable (Article 330), 
and lead-sheathed cable. 

(3) Tag Marking. The following conductors and cables 
shall be marked by means of a printed tag attached to the 
coil, reel, or carton: 

(1) Mineral-insulated, metal-sheathed cable 

(2) Switchboard wires 

(3) Metal-covered, single-conductor cables 

(4) Type AC cable 

(4) Optional Marking of Wire Size. The information re- 
quired in 310.11(A)(4) shall be permitted to be marked on 
the surface of the individual insulated conductors for the 
following multiconductor cables: 

(1) Type MC cable 

(2) Tray cable 

(3) Irrigation cable 

(4) Power-limited tray cable 

(5) Power-limited fire alarm cable 

(6) Instrumentation tray cable 

(C) Suffixes to Designate Number of Conductors. A type 
letter or letters used alone shall indicate a single insulated 
conductor. The letter suffixes shall be indicated as follows: 

(1) D — For two insulated conductors laid parallel within 
an outer nonmetallic covering 

(2) M — For an assembly of two or more insulated con- 
ductors twisted spirally within an outer nonmetallic 
covering 

(D) Optional Markings. All conductors and cables con- 
tained in Chapter 3 shall be permitted to be surface marked 
to indicate special characteristics of the cable materials. 
These markings include, but are not limited to, markings 
for limited smoke, sunlight resistant, and so forth. 

310.12 Conductor Identification. 

(A) Grounded Conductors. Insulated or covered 
grounded conductors shall be identified in accordance with 
200.6. 

(B) Equipment Grounding Conductors. Equipment 
grounding conductors shall be in accordance with 250.119. 

(C) Ungrounded Conductors. Conductors that are in- 
tended for use as ungrounded conductors, whether used as a 
single conductor or in multiconductor cables, shall be fin- 
ished to be clearly distinguishable from grounded and 
grounding conductors. Distinguishing markings shall not 



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ARTICLE 310 — CONDUCTORS FOR GENERAL WIRING 



70-137 



conflict in any manner with the surface markings required 
by 310.11(B)(1). 

Exception: Conductor identification shall be permitted in 
accordance with 200.7. 

310.13 Conductor Constructions and Applications. 

Insulated conductors shall comply with the applicable pro- 
visions of one or more of the following: Tables 310.13, 
310.61, 310.62, 310.63, and 310.64. 

Table 310.13 Conductor Application and Insulations 



These conductors shall be permitted for use in any of 
the wiring methods recognized in Chapter 3 and as speci- 
fied in their respective tables. 

FPN: Thermoplastic insulation may stiffen at temperatures 
lower than minus 10°C (plus 14°F). Thermoplastic insula- 
tion may also be deformed at normal temperatures where 
subjected to pressure, such as at points of support. Thermo- 
plastic insulation, where used on dc circuits in wet loca- 
tions, may result in electroendosmosis between conductor 
and insulation. 







Maximum 
Operating 






Thickness of Insulation 


























Type 


Tempera- 


Application 




AWGor 










Outer 


Trade Name 


Letter 


ture 


Provisions 


Insulation 


kcmil 


mm 




Mils 




Covering 1 


Fluorinated 


FEPor 


90°C 


Dry and damp 


Fluorinated 


14-10 


0.51 




20 




None 


ethylene 
propylene 


FEPB 


194°F 


locations 


ethylene 
propylene 


8-2 


0.76 




30 












14-8 


0.36 


14 


Glass braid 






200 C 


Dry locations — 


Fluorinated 


















392°F 


special 
applications 2 


ethylene 
propylene 


6-2 


0.36 




14 




Glass or 
other 
suitable 
braid 
material 


Mineral 


MI 


90°C 


Dry and wet 


Magnesium 


18-16 3 


0.58 




23 




Copper or 


insulation 




194°F 


locations 


oxide 


16-10 


0.91 




36 




alloy 


(metal 










9-4 


1.27 




50 




steel 


sheathed) 




250°C 
482°F 


For special 
applications 




3-500 


1.40 




55 






Moisture-, 


MTW 


60°C 


Machine tool 


Flame- 




(A) (B) 


(A) 




(B) 


(A) None 


heat-, and 




HOT 


wiring in wet 


retardant 












(B) Nylon 


oil-resistant 






locations as 


moisture-, 












jacket or 


thermoplastic 




90°C 
194°F 


permitted in 
NFPA 79 (See 
Article 670.) 
Machine tool 
wiring in dry 
locations as 
permitted in 
NFPA 79 (See 
Article 670.) 


heat-, and 
oil- 
resistant 
thermo- 
plastic 


22-12 

10 

8 

6 

4-2 

1-4/0 

213-500 

501-1000 


0.76 0.38 
0.76 0.51 
1.14 0.76 
1.52 0.76 
1.52 1.02 
2.03 1.27 
2.41 1.52 
2.79 1.78 


30 
30 
45 
60 
60 
80 
95 
110 




15 
20 
30 
30 
40 
50 
60 
70 


equivalent 


Paper 




85°C 
185°F 


For underground 
service 

conductors, or 
by special 
permission 


Paper 












Lead 
sheath 


Perfluoro- 


PFA 


90°C 


Dry and damp 


Perfluoro- 


14-10 


0.51 




20 




None 


alkoxy 




194°F 

200°C 
392°F 


locations 

Dry locations — 

special 

applications 2 


alkoxy 


8-2 
1-4/0 


0.76 
1.14 




30 

45 







NATIONAL ELECTRICAL CODE 



2002 Edition 



70-138 



ARTICLE 310 — CONDUCTORS FOR GENERAL WIRING 



Table 310.13 Continued 







Maximum 






Thickness of Insulation 








Operating 


























Type 


Tempera- 


Application 




AWGor 






Outer 


Trade Name 


Letter 


ture 


Provisions 


Insulation 


kcmil 


mm 


Mils 


Covering 1 


Perfluoro- 


PFAH 


250°C 


Dry locations only. 


Perfluoro- 


14-10 


0.51 


20 


None 


alkoxy 




482°F 


Only for leads 
within apparatus 
or within 
raceways 
connected to 
apparatus (nickel 
or nickel-coated 
copper only) 


alkoxy 


8-2 
1-4/0 


0.76 
1.14 


30 

45 




Thermoset 


RHH 


90°C 


Dry and damp 




14-10 


1.14 


45 


Moisture- 






194°F 


locations 




8-2 

1-4/0 

213-500 

501-1000 

1001-2000 

For 

601-2000, 

see Table 

310.62. 


1.52 
2.03 
241 
2.79 
3.18 


60 
80 
95 
110 
125 


resistant, 

flame- 

retardant, 

nonmetallic 

covering 1 


Moisture- 


RHW 4 


75°C 


Dry and wet 


Flame- 


14-10 


1.14 


45 


Moisture- 


resistant 




167°F 


locations 


retardant, 


8-2 


1.52 


60 


resistant, 


thermoset 








moisture- 


1-4/0 


2.03 


80 


flame- 










resistant 


213-500 


2.41 


95 


retardant, 










thermo- 


501-1000 


2.79 


110 


nonmetallic 










set 


1001-2000 

For 

601-2000, 

see Table 

310.62. 


3.18 


125 


covering 5 


Moisture- 


RHW-2 


90°C 


Dry and wet 


Flame- 


14-10 


1.14 


45 


Moisture- 


resistant 




194°F 


locations 


retardant 


8-2 


1.52 


60 


resistant, 


thermoset 








moisture- 


1-4/0 


2.03 


80 


flame- 










resistant 


213-500 


2.41 


95 


retardant, 










thermo- 


501-1000 


2.79 


110 


nonmetallic 










set 


1001-2000 

For 

601-2000, 

see Table 

310.62. 


3.18 


125 


covering 5 


Silicone 


SA 


90°C 


Dry and damp 




14-10 


1.14 


45 


Glass or 






194°F 


locations 




8-2 

1-4/0 

213-500 


1.52 
2.03 
2.41 


60 
80 
95 


other 

suitable 

braid 






200°C 


For special 


Silicone 


501-1000 


2.79 


110 


material 






392°F 


application 


rubber 


1001-2000 


3.18 


125 




Thermoset 


SIS 


90°C 


Switchboard wiring 


Flame- 


14-10 


0.76 


30 


None 






194°F 


only 


retardant 
thermoset 


8-2 
1-4/0 


1.14 

2.41 


45 
95 





2002 Edition 



NATIONAL ELECTRICAL CODE 



ARTICLE 310 — CONDUCTORS FOR GENERAL WIRING 



70-139 



Table 310.13 Continued 







Maximum 
Operating 






Thickness of Insulation 






















Type 


Tempera- 


Application 




AWGor 






Outer 


Trade Name 


Letter 


ture 


Provisions 


Insulation 


kcmil 


mm 


Mils 


Covering 1 


Thermoplastic 


TBS 


90°C 


Switchboard wiring 


Thermo- 


14-10 


0.76 


30 


Flame- 


and fibrous 




194°F 


only 


plastic 


8 


1.14 


45 


retardant, 


outer braid 










6-2 
1-4/0 


1.52 
2.03 


60 
80 


nonmetallic 
covering 


Extended 


TFE 


250°C 


Dry locations only. 


Extruded 


14-10 


0.51 


20 


None 


polytetra- 




482°F 


Only for leads 


polytetra- 


8-2 


0.76 


30 




fluoro- 






within apparatus 


fluoro- 


1-4/0 


1.14 


45 




ethylene 






or within 
raceways 
connected to 
apparatus, or as 
open wiring 
(nickel or 
nickel-coated 
copper only) 


ethylene 










Heatresistant 


THHN 


90°C 


Dry and damp 


Flame- 


14-12 


0.38 


15 


Nylon 


thermoplastic 




194°F 


locations 


retardant, 


10 


0.51 


20 


jacket or 










heat- 


8-6 


0.76 


30 


equivalent 










resistant 


4-2 


1.02 


40 












thermo- 


1-4/0 


1.27 


50 












plastic 


250-500 
501-1000 


1.52 
1.78 


60 
70 




Moisture- and 


THHW 


75°C 


Wet location 


Flame- 


14-10 


0.76 


30 


None 


heat-resistant 




167°F 




retardant, 


8 


1.14 


45 




thermoplastic 




90°C 


Dry location 


moisture- 


6-2 


1.52 


60 








194°F 




and heat- 
resistant 
thermo- 
plastic 


1-4/0 
213-500 
501-1000 


2.03 
2.41 
2.79 


80 
95 
110 




Moisture- and 


THW 4 


75°C 


Dry and wet 


Flame- 


14-10 


0.76 


30 


None 


heat-resistant 




167°F 


locations 


retardant, 


8 


1.14 


45 




thermoplastic 








moisture- 


6-2 


1.52 


60 








90°C 


Special 


and 


1-4/0 


2.03 


80 








194°F 


applications 


heat- 


213-500 


2.41 


95 










within electric 


resistant 


501-1000 


2.79 


110 










discharge 


thermo- 


1001-2000 


3.18 


125 










lighting 


plastic 
















equipment. 


















Limited to 1000 


















open-circuit 


















volts or less. 


















(size 14-8 only 


















as permitted in 


















410.33) 












Moisture- 


THWN 4 


75°C 


Dry and wet 


Flame- 


14-12 


0.38 


15 


Nylon 


and 




167°F 


locations 


retardant, 


10 


0.51 


20 


jacket or 


heat-resistant 








moisture- 


8-6 


0.76 


30 


equivalent 


thermoplastic 








and heat- 
resistant 
thermo- 
plastic 


4-2 

1-4/0 

250-500 

501-1000 


1.02 
1.27 
1.52 
1.78 


40 
50 
60 
70 





NATIONAL ELECTRICAL CODE 



2002 Edition 



70-140 



ARTICLE 310 — CONDUCTORS FOR GENERAL WIRING 



Table 310.13 Continued 







Maximum 
Operating 






Thickness of Insulation 






















Type 


Tempera- 


Application 




AWG or 






Outer 


Trade Name 


Letter 


ture 


Provisions 


Insulation 


kcmil 


mm 


Mils 


Covering 1 


Moisture- 


TW 


60°C 


Dry and wet 


Flame- 


14-10 


0.76 


30 


None 


resistant 




140°F 


locations 


retardant, 


8 


1.14 


45 




thermo- 








moisture- 


6-2 


1.52 


60 




plastic 








resistant 
thermo- 
plastic 


1-4/0 

213-500 

501-1000 

1001-2000 


2.03 
2.41 
2.79 
3.18 


80 
95 
110 

125 




Underground 


UF 


60°C 


See Article 340. 


Moisture- 


14-10 


1.52 


60 6 


Integral 


feeder and 




140°F 




resistant 


8-2 


2.03 


80 6 


with 


branch- 




75°C 






1-4/0 


2.41 


95 6 


insulation 


circuit cable 




167°F 7 




Moisture- 










— single 








and heat- 










conductor 








resistant 










(For Type UF 


















cable 


















employing 


















more than 


















one 


















conductor, 


















see Articles 


















339, 340.) 


















Underground 


USE 4 


75°C 


See Article 338. 


Heat- and 


14-10 


1.14 


45 


Moisture- 


service- 




167°F 




moisture- 


8-2 


1.52 


60 


resistant 


entrance 








resistant 


1-4/0 


2.03 


80 


nonmetallic 


cable — 










213-500 


2.41 


95 8 


covering 


single 










501-1000 


2.79 


110 


(See 


conductor 










1001-2000 


3.18 


125 


338.2.) 


(For Type 


















USE cable 


















employing 


















more than 


















one 


















conductor, 


















see Article 


















338.) 


















Thermoset 


XHH 


90°C 


Dry and damp 


Flame- 


14-10 


0.76 


30 


None 






194°F 


locations 


retardant 
thermoset 


8-2 

1-4/0 

213-500 

501-1000 

1001-2000 


1.14 
1.40 
1.65 
2.03 
2.41 


45 
55 
65 
80 
95 




Moisture- 


XHHW 4 


90°C 


Dry and damp 


Flame- 


14-10 


0.76 


30 


None 


resistant 




194°F 


locations 


retardant, 


8-2 


1.14 


45 




thermoset 








moisture- 


1-4/0 


1.40 


55 








75°C 


Wet locations 


resistant 


213-500 


1.65 


65 








167°F 




thermoset 


501-1000 
1001-2000 


2.03 
2.41 


80 
95 





2002 Edition 



NATIONAL ELECTRICAL CODE 



ARTICLE 310 — CONDUCTORS FOR GENERAL WIRING 



70-141 



Table 310.13 Continued 







Maximum 
Operating 






Thickness of Insulation 






















Type 


Tempera- 


Application 




AWGor 






Outer 


Trade Name 


Letter 


ture 


Provisions 


Insulation 


kcmil 


mm 


Mils 


Covering 1 


Moisture- 


XHHW-2 


90°C 


Dry and wet 


Flame- 


14-10 


0.76 


30 


None 


resistant 




194°F 


locations 


retardant, 


8-2 


1.14 


45 




thermoset 








moisture- 
resistant 
thermoset 


1-4/0 

213-500 

501-1000 

1001-2000 


1.40 
1.65 

2.03 
2.41 


55 
65 
80 
95 




Modified 


Z 


90°C 


Dry and damp 


Modified 


14-12 


0.38 


15 


None 


ethylene 




194°F 


locations 


ethylene 


10 


0.51 


20 




tetra- 








tetra- 


8-4 


0.64 


25 




fluoro- 




150°C 


Dry locations — 


fluoro- 


3-1 


0.89 


35 




ethylene 




302°F 


special 
applications 2 


ethylene 


1/0-4/0 


1.14 


45 




Modified 


ZW 4 


75°C 


Wet locations 


Modified 


14-10 


0.76 


30 


None 


ethylene 




167°F 




ethylene 


8-2 


1.14 


45 




tetra- 








tetra- 










fluoro- 




90°C 


Dry and damp 


fluoro- 










ethylene 




194°F 

150°C 
302°F 


locations 

Dry locations — 
special 
applications 2 


ethylene 











Some insulations do not require an outer covering. 

2 Where design conditions require maximum conductor operating temperatures above 90°C (194°F). 

3 For signaling circuits permitting 300-volt insulation. 

4 Listed wire types designated with the suffix "2," such as RHW-2, shall be permitted to be used at a continuous 
90°C (194°F) operating temperature, wet or dry. 

5 Some rubber insulations do not require an outer covering. 

6 Includes integral jacket. 

7 For ampacity limitation, see 340.80. 

8 Insulation thickness shall be permitted to be 2.03 mm (80 mils) for listed Type USE conductors that have been 

subjected to special investigations. The nonmetallic covering over individual rubber-covered conductors of aluminum-sheathed 
cable and of lead-sheathed or multiconductor cable shall not be required to be flame retardant. 
For Type MC cable, see 330.104. For nonmetallic-sheathed cable, see Article 334, 
Part III. For Type UF cable, see Article 340, Part III. 



310.14 Aluminum Conductor Material. Solid aluminum 
conductors 8, 10, and 12 AWG shall be made of an AA- 
8000 series electrical grade aluminum alloy conductor ma- 
terial. Stranded aluminum conductors 8 AWG through 1000 
kcmil marked as Type RHH, RHW, XHHW, THW, THHW, 
THWN, THHN, service-entrance Type SE Style U and SE 
Style R shall be made of an AA-8000 series electrical grade 
aluminum alloy conductor material. 

310.15 Ampacities for Conductors Rated 0-2000 Volts. 
(A) General. 

(1) Tables or Engineering Supervision. Ampacities for 
conductors shall be permitted to be determined by tables or 



under engineering supervision, as provided in 310.15(B) 
and (C). 

FPN No. 1: Ampacities provided by this section do not 
take voltage drop into consideration. See 210.19(A), FPN 
No. 4, for branch circuits and 215.2(D), FPN No. 2, for 
feeders. 

FPN No. 2: For the allowable ampacities of Type MTW 
wire, see Table 11 in NFPA 79-1997, Electrical Standard 
for Industrial Machinery. 

(2) Selection of Ampacity. Where more than one calcu- 
lated or tabulated ampacity could apply for a given circuit 
length, the lowest value shall be used. 



NATIONAL ELECTRICAL CODE 



2002 Edition 



70-142 



ARTICLE 310 — CONDUCTORS FOR GENERAL WIRING 



Exception: Where two different ampacities apply to adja- 
cent portions of a circuit, the higher ampacity shall be 
permitted to be used beyond the point of transition, a dis- 
tance equal to 3.0 m (10 ft) or 10 percent of the circuit 
length figured at the higher ampacity, whichever is less. 

FPN: See 110.14(C) for conductor temperature limitations 
due to termination provisions. 

(B) Tables. Ampacities for conductors rated to 2000 
volts shall be as specified in the Allowable Ampacity Tables 
310.16 through 310.19, and Ampacity Tables 310.20 and 
310.21, as modified by (1) through (6). 

FPN: Tables 310.16 through 310.19 are application tables 
for use in determining conductor sizes on loads calculated 
in accordance with Article 220. Allowable ampacities result 
from consideration of one or more of the following: 

(1) Temperature compatibility with connected equipment, 
especially the connection points. 

(2) Coordination with circuit and system overcurrent pro- 
tection. 

(3) Compliance with the requirements of product listings 
or certifications. See 110.3(B). 

(4) Preservation of the safety benefits of established indus- 
try practices and standardized procedures. 

(1) General. For explanation of type letters used in tables 
and for recognized sizes of conductors for the various con- 
ductor insulations, see 310.13. For installation require- 
ments, see 310.1 through 310.10 and the various articles of 
this Code. For flexible cords, see Tables 400.4, 400.5(A), 
and 400.5(B). 

(2) Adjustment Factors. 

(a) More Than Three Current-Carrying Conductors in 
a Raceway or Cable. Where the number of current-carrying 
conductors in a raceway or cable exceeds three, or where 
single conductors or multiconductor cables are stacked or 
bundled longer than 600 mm (24 in.) without maintaining 
spacing and are not installed in raceways, the allowable 
ampacity of each conductor shall be reduced as shown in 
Table 310.15(B)(2)(a). 

FPN: See Annex B, Table B. 3 10.11, for adjustment factors 
for more than three current-carrying conductors in a race- 
way or cable with load diversity. 

Exception No. 1: Where conductors of different systems, as 
provided in 300.3, are installed in a common raceway or 
cable, the derating factors shown in Table 310.15(B)(2)(a) 
shall apply to the number of power and lighting conductors 
only (Articles 210, 215, 220, and 230). 

Exception No. 2: For conductors installed in cable trays, 
the provisions of 392. 11 shall apply. 



Exception No. 3: Derating factors shall not apply to con- 
ductors in nipples having a length not exceeding 600 mm 
(24 in.). 

Exception No. 4: Derating factors shall not apply to un- 
derground conductors entering or leaving an outdoor 
trench if those conductors have physical protection in the 
form of rigid metal conduit, intermediate metal conduit, or 
rigid nonmetallic conduit having a length not exceeding 
3.05 m (10 ft) and if the number of conductors does not 
exceed four. 

Exception No. 5: Adjustment factors shall not apply to 
Type AC cable or to Type MC cable without an overall 
outer jacket under the following conditions: 

(a) Each cable has not more than three current- carrying 
conductors. 

(b) The conductors are 12 AWG copper. 

(c) Not more than 20 current-carrying conductors are 
bundled, stacked, or supported on "bridle rings. " 

A 60 percent adjustment factor shall be applied where the 
current-carrying conductors in these cables that are 
stacked or bundled longer than 600 mm (24 in.) without 
maintaining spacing exceeds 20. 

(b) More Than One Conduit, Tube, or Raceway. Spacing 
between conduits, tubing, or raceways shall be maintained. 

Table 310.15(B)(2)(a) Adjustment Factors for More Than 
Three Current-Carrying Conductors in a Raceway or Cable 





Percent of Values in 




Tables 310.16 through 


Number of 


310.19 as Adjusted for 


Current-Carrying 


Ambient Temperature if 


Conductors 


Necessary 


4-6 


80 


7-9 


70 


10-20 


50 


21-30 


45 


31-40 


40 


41 and above 


35 



(3) Bare or Covered Conductors. Where bare or covered 
conductors are used with insulated conductors, their allow- 
able ampacities shall be limited to those permitted for the 
adjacent insulated conductors. 

(4) Neutral Conductor. 

(a) A neutral conductor that carries only the unbal- 
anced current from other conductors of the same circuit 
shall not be required to be counted when applying the pro- 
visions of 310.15(B)(2)(a). 



2002 Edition 



NATIONAL ELECTRICAL CODE 



ARTICLE 310 — CONDUCTORS FOR GENERAL WIRING 



70-143 



• 



• 



• 



(b) In a 3-wire circuit consisting of two phase wires 
and the neutral of a 4-wire, 3-phase, wye-connected sys- 
tem, a common conductor carries approximately the same 
current as the line-to-neutral load currents of the other con- 
ductors and shall be counted when applying the provisions 
of 310.15(B)(2)(a). 

(c) On a 4-wire, 3-phase wye circuit where the major 
portion of the load consists of nonlinear loads, harmonic 
currents are present in the neutral conductor; the neutral 
shall therefore be considered a current-carrying conductor. 

(5) Grounding or Bonding Conductor. A grounding or 
bonding conductor shall not be counted when applying the 
provisions of 310.15(B)(2)(a). 

(6) 120/240- Volt, 3-Wire, Single-Phase Dwelling Ser- 
vices and Feeders. For dwelling units, conductors, as listed 
in Table 310.15(B)(6), shall be permitted as 120/240-volt, 
3-wire, single-phase service-entrance conductors, service 
lateral conductors, and feeder conductors that serve as the 
main power feeder to a dwelling unit and are installed in 
raceway or cable with or without an equipment grounding 
conductor. For application of this section, the main power 
feeder shall be the feeder(s) between the main disconnect 
and the lighting and appliance branch-circuit panelboard(s). 
The feeder conductors to a dwelling unit shall not be re- 
quired to be larger than their service-entrance conductors. 
The grounded conductor shall be permitted to be smaller 
than the ungrounded conductors, provided the requirements 
of 215.2, 220.22, and 230.42 are met. 

(C) Engineering Supervision. Under engineering supervi- 
sion, conductor ampacities shall be permitted to be calcu- 
lated by means of the following general formula: 



Table 310.15(B)(6) Conductor Types and Sizes 
for 120/240- Volt, 3-Wire, Single-Phase Dwelling 
Services and Feeders. Conductor Types RHH, RH W, 
RHW-2, THHN, THHW, THW, THW-2, THWN, THWN-2, 
XHH W, XHHW-2, SE, USE, USE-2 

Conductor (AWG or kcmil) 





Aluminum or 


Service or 




Copper-Clad 


Feeder Rating 


Copper 


Aluminum 


(Amperes) 


4 


2 


100 


3 


1 


110 


2 


1/0 


125 


1 


2/0 


150 


1/0 


3/0 


175 


2/0 


4/0 


200 


3/0 


250 


225 


4/0 


300 


250 


250 


350 


300 


350 


500 


350 


400 


600 


400 



/ = 



ITC-jTA + ATD) 
RDC{1 + YC)RCA 



where: 
TC = conductor temperature in degrees Celsius (°C) 
TA = ambient temperature in degrees Celsius (°C) 
AID = dielectric loss temperature rise 
RDC = dc resistance of conductor at temperature TC 
YC = component ac resistance resulting from skin 
effect and proximity effect 
RCA = effective thermal resistance between conductor 
and surrounding ambient 

FPN: See Annex B for examples of formula applications. 



NATIONAL ELECTRICAL CODE 



2002 Edition 



70-144 



ARTICLE 310 — CONDUCTORS FOR GENERAL WIRING 



Table 310.16 Allowable Ampacities of Insulated Conductors Rated Through 2000 Volts, 60°C Through 90°C 
(140°F Through 194°F), Not More Than Three Current-Carrying Conductors in Raceway, Cable, 
or Earth (Directly Buried), Based on Ambient Temperature of 30°C (86°F) 





Temperature Rating of Conductor (See Table 310.13.) 






60°C 


75°C 


90°C 


60°C 


75°C 


90°C 






(140°F) 


(167°F) 


(194°F) 


(140°F) 


(167°F) 


(194°F) 










Types TBS, SA, SIS, 
















FEP, FEPB, MI, RHH, 






Types TBS, SA, SIS, 










RHW-2, THHN, 






THHN, THHW, 








Types RHW, 


THHW, THW-2, 




Types RHW, 


THW-2, THWN-2, 








THHW, THW, 


THWN-2, USE-2, XHH, 




THHW, THW, 


RHH, RHW-2, USE-2, 






Types TW, 


THWN, XHHW, 


XHHW, XHHW-2, 


Types TW, 


THWN, XHHW, 


XHH, XHHW, 






UF 


USE, ZW 


ZW-2 


UF 


USE 


XHHW-2, ZW-2 




Size AWG or 














Size AWG or 










kcmil 




COPPER 


ALUMINUM OR COPPER-CLAD ALUMINUM 


kcmil 


18 






14 










16 


— 


— 


18 


— 











14* 


20 


20 


25 


— 


— 


— 


— 


12* 


25 


25 


30 


20 


20 


25 


12* 


10* 


30 


35 


40 


25 


30 


35 


10* 


8 


40 


50 


55 


30 


40 


45 


8 


6 


55 


65 


75 


40 


50 


60 


6 


4 


70 


85 


95 


55 


65 


75 


4 


3 


85 


100 


no 


65 


75 


85 


3 


2 


95 


115 


130 


75 


90 


100 


2 


1 


110 


130 


150 


85 


100 


115 


1 


1/0 


125 


150 


170 


100 


120 


135 


1/0 


2/0 


145 


175 


195 


115 


135 


150 


2/0 


3/0 


165 


200 


225 


130 


155 


175 


3/0 


4/0 


195 


230 


260 


150 


180 


205 


4/0 


250 


215 


255 


290 


170 


205 


230 


250 


300 


240 


285 


320 


190 


230 


255 


300 


350 


260 


310 


350 


210 


250 


280 


350 


400 


280 


335 


380 


225 


270 


305 


400 


500 


320 


380 


430 


260 


310 


350 


500 


600 


355 


420 


475 


285 


340 


385 


600 


700 


385 


460 


520 


310 


375 


420 


700 


750 


400 


475 


535 


320 


385 


435 


750 


800 


410 


490 


555 


330 


395 


450 


800 


900 


435 


520 


585 


355 


425 


480 


900 


1000 


455 


545 


615 


375 


445 


500 


1000 


1250 


495 


590 


665 


405 


485 


545 


1250 


1500 


520 


625 


705 


435 


520 


585 


1500 


1750 


545 


650 


735 


455 


545 


615 


1750 


2000 


560 


665 


750 


470 


560 


630 


2000 



CORRECTION FACTORS 



Ambient 
Temp. 

(°C) 


For ambient temperatures other than 30°C (86°F), multiply the allowable ampacities shown above by the appropriate 

factor shown below. 


Ambient 
Temp. (°F) 


21-25 


1.08 


1.05 


1.04 


1.08 


1.05 


1.04 


70-77 


26-30 


1.00 


1.00 


1.00 


1.00 


1.00 


1.00 


78-86 


31-35 


0.91 


0.94 


0.96 


0.91 


0.94 


0.96 


87-95 


36-40 


0.82 


0.88 


0.91 


0.82 


0.88 


0.91 


96-104 


41-45 


0.71 


0.82 


0.87 


0.71 


0.82 


0.87 


105-113 


46-50 


0.58 


0.75 


0.82 


0.58 


0.75 


0.82 


114-122 


51-55 


0.41 


0.67 


0.76 


0.41 


0.67 


0.76 


123-131 


56-60 


— 


0.58 


0.71 


— 


0.58 


0.71 


132-140 


61-70 


— 


0.33 


0.58 


— 


0.33 


0.58 


141-158 


71-80 


— 


— 


0.41 


— 


— 


0.41 


159-176 



• 



See 240.4(D). 



2002 Edition 



NATIONAL ELECTRICAL CODE 



ARTICLE 310 — CONDUCTORS FOR GENERAL WIRING 



70-145 



Table 310.17 Allowable Ampacities of Single-Insulated Conductors Rated Through 2000 Volts 
in Free Air, Based on Ambient Air Temperature of 30°C (86°F) 



• 



• 





Temperature Rating of Conductor (See Table 310.13.) 






60°C 


75°C 


90°C 


60°C 


75°C 


90°C 






(140°F) 


(167°F) 


(194°F) 


(140°F) 


(167°F) 


(194°F) 










Types TBS, SA, SIS, 
















FEP, FEPB, MI, 






Types TBS, SA, SIS, 








Types 


RHH, RHW-2, 




Types 


THHN, THHW, 








RHW, 


THHN, THHW, 




RHW, 


THW-2, THWN-2, 








THHW, 


THW-2, THWN-2, 




THHW, 


RHH, RHW-2, 








THW, 


USE-2, XHH, 




THW, 


USE-2, XHH, 






Types TW, 


THWN, 


XHHW, XHHW-2, 


Types TW, 


THWN, 


XHHW, XHHW-2, 






UF 


XHHW, ZW 


ZW-2 


UF 


XHHW 


ZW-2 




Size AWG 








ALUMINUM OR COPPER-CLAD 


Size AWG 


or kcmil 




COPPER 




ALUMINUM 


or kcmil 


18 






18 










16 


— 


— 


24 


— 


— 


— 


— 


14* 


25 


30 


35 


— 


— 


— 


— 


12* 


30 


35 


40 


25 


30 


35 


12* 


10* 


40 


50 


55 


35 


40 


40 


10* 


8 


60 


70 


80 


45 


55 


60 


8 


6 


80 


95 


105 


60 


75 


80 


6 


4 


105 


125 


140 


80 


100 


110 


4 


3 


120 


145 


165 


95 


115 


130 


3 


2 


140 


170 


190 


110 


135 


150 


2 


1 


165 


195 


220 


130 


155 


175 


1 


1/0 


195 


230 


260 


150 


180 


205 


1/0 


2/0 


225 


265 


300 


175 


210 


235 


2/0 


3/0 


260 


310 


350 


200 


240 


275 


3/0 


4/0 


300 


360 


405 


235 


280 


315 


4/0 


250 


340 


405 


455 


265 


315 


355 


250 


300 


375 


445 


505 


290 


350 


395 


300 


350 


420 


505 


570 


330 


395 


445 


350 


400 


455 


545 


615 


355 


425 


480 


400 


500 


515 


620 


700 


405 


485 


545 


500 


600 


575 


690 


780 


455 


540 


615 


600 


700 


630 


755 


855 


500 


595 


675 


700 


750 


655 


785 


885 


515 


620 


700 


750 


800 


680 


815 


920 


535 


645 


725 


800 


900 


730 


870 


985 


580 


700 


785 


900 


1000 


780 


935 


1055 


625 


750 


845 


1000 


1250 


890 


1065 


1200 


710 


855 


960 


1250 


1500 


980 


1175 


1325 


795 


950 


1075 


1500 


1750 


1070 


1280 


1445 


875 


1050 


1185 


1750 


2000 


1155 


1385 


1560 


960 


1150 


1335 


2000 



• 



NATIONAL ELECTRICAL CODE 



2002 Edition 



70-146 



ARTICLE 310 — CONDUCTORS FOR GENERAL WIRING 



Table 310.17 Continued 



Size AWG 
or kcmil 



Temperature Rating of Conductor (See Table 310.13.) 



60°C 
(140°F) 



Types TW, 
UF 



75°C 
(167°F) 



Types 

RHW, 
THHW, 

THW, 

THWN, 

XHHW, ZW 



90°C 
(194°F) 



Types TBS, SA, SIS, 

FEP, FEPB, MI, 

RHH, RHW-2, 

THHN, THHW, 

THW-2, THWN-2, 

USE-2, XHH, 

XHHW, XHHW-2, 

ZW-2 



COPPER 



60°C 
(140°F) 



Types TW, 
UF 



75°C 
(167°F) 



Types 

RHW, 

THHW, 

THW, 

THWN, 

XHHW 



90°C 
(194°F) 



Types TBS, SA, SIS, 

THHN, THHW, 

THW-2, THWN-2, 

RHH, RHW-2, 

USE-2, XHH, 

XHHW, XHHW-2, 

ZW-2 



ALUMINUM OR COPPER-CLAD 
ALUMINUM 



CORRECTION FACTORS 



Size AWG 
or kcmil 



Ambient 
Temp. 

(°C) 


For ambient 


temperatures other than 30°C (86°F), multiply the allowable ampacities shown above 
by the appropriate factor shown below. 


Ambient 
Temp. (°F) 


21-25 


1.08 


1.05 


1.04 


1.08 


1.05 


1.04 


70-77 


26-30 


1.00 


1.00 


1.00 


1.00 


1.00 


1.00 


78-86 


31-35 


0.91 


0.94 


0.96 


0.91 


0.94 


0.96 


87-95 


36-40 


0.82 


0.88 


0.91 


0.82 


0.88 


0.91 


96-104 


41-45 


0.71 


0.82 


0.87 


0.71 


0.82 


0.87 


105-113 


46-50 


0.58 


0.75 


0.82 


0.58 


0.75 


0.82 


114-122 


51-55 


0.41 


0.67 


0.76 


0.41 


0.67 


0.76 


123-131 


56-60 


— 


0.58 


0.71 


— 


0.58 


0.71 


132-140 


61-70 


— 


0.33 


0.58 


— 


0.33 


0.58 


141-158 


71-80 


— 


— 


0.41 


— 


— 


0.41 


159-176 



• 



* See 240.4(D). 



2002 Edition 



NATIONAL ELECTRICAL CODE 



ARTICLE 310 — CONDUCTORS FOR GENERAL WIRING 



70-147 



Table 310.18 Allowable Ampacities of Insulated Conductors Rated Through 2000 Volts, 

150°C Through 250°C (302°F Through 482°F). Not More Than Three Current-Carrying Conductors 

in Raceway or Cable, Based on Ambient Air Temperature of 40°C (104°F) 





Temperature Rating of Conductor (See Table 310.13.) 






150°C (302°F) 


200°C (392°F) 


250°C (482°F) 


150°C (302°F) 






TypeZ 


Types FEP, FEPB, 
PFA 


Types PFAH, TFE 


TypeZ 




Size AWG or kcmil 


COPPER 


NICKEL OR 

NICKEL-COATED 

COPPER 


ALUMINUM OR 

COPPER-CLAD 

ALUMINUM 


Size AWG or kcmil 


14 

12 

10 

8 


34 
43 
55 
76 


36 
45 
60 
83 


39 
54 
73 
93 


30 
44 
57 


14 

12 

10 

8 


6 

4 
3 
2 
1 


96 
120 
143 
160 
186 


110 

125 
152 
171 
197 


117 
148 
166 
191 
215 


75 

94 

109 

124 
145 


6 
4 

3 
2 
1 


1/0 
2/0 
3/0 
4/0 


215 
251 
288 
332 


229 
260 
297 
346 


244 
273 
308 
361 


169 
198 

227 
260 


1/0 
2/0 
3/0 
4/0 



CORRECTION FACTORS 



Ambient Temp. 

(°C) 


For ambient temperatures other than 40°C (104°F), multiply the allowable 
ampacities shown above by the appropriate factor shown below. 


Ambient Temp. 

(°F) 


41-50 


0.95 


0.97 


0.98 


0.95 


105-122 


51-60 


0.90 


0.94 


0.95 


0.90 


123-140 


61-70 


0.85 


0.90 


0.93 


0.85 


141-158 


71-80 


0.80 


0.87 


0.90 


0.80 


159-176 


81-90 


0.74 


0.83 


0.87 


0.74 


177-194 


91-100 


0.67 


0.79 


0.85 


0.67 


195-212 


101-120 


0.52 


0.71 


0.79 


0.52 


213-248 


121-140 


0.30 


0.61 


0.72 


0.30 


249-284 


141-160 


— 


0.50 


0.65 


— 


285-320 


161-180 


— 


0.35 


0.58 


— 


321-356 


181-200 


— 


— 


0.49 


— 


357-392 


201-225 


— 


— 


0.35 


— 


393^37 



NATIONAL ELECTRICAL CODE 



2002 Edition 



70-148 



ARTICLE 310 — CONDUCTORS FOR GENERAL WIRING 



Table 310.19 Allowable Ampacities of Single-Insulated Conductors, Rated Through 2000 Volts, 

150°C Through 250°C (302°F Through 482°F), in Free Air, Based on Ambient Air Temperature of 40°C (104°F) 





Temperature Rating of Conductor (See Table 310.13.) 






150°C (302°F) 


200°C (392°F) 


250°C (482°F) 


150°C (302°F) 








Types FEP, 










TypeZ 


FEPB, PFA 


Types PFAH, TFE 


TypeZ 








NICKEL, OR 


ALUMINUM OR 




Size AWG or 




NICKEL-COATED 


COPPER-CLAD 




kcmil 


COPPER 


COPPER 


ALUMINUM 


Size AWG or kcmil 


14 


46 


54 


59 





14 


12 


60 


68 


78 


47 


12 


10 


80 


90 


107 


63 


10 


8 


106 


124 


142 


83 


8 


6 


155 


165 


205 


112 


6 


4 


190 


220 


278 


148 


4 


3 


214 


252 


327 


170 


3 


2 


255 


293 


381 


198 


2 


1 


293 


344 


440 


228 


1 


1/0 


339 


399 


532 


263 


1/0 


2/0 


390 


467 


591 


305 


2/0 


3/0 


451 


546 


708 


351 


3/0 


4/0 


529 


629 


830 


411 


4/0 



CORRECTION FACTORS 



Ambient Temp. 

(°C) 


For ambient temperatures other than 40°C (104°F), multiply the allowable 
ampacities shown above by the appropriate factor shown below. 


Ambient Temp. 

(°F) 


41-50 


0.95 


0.97 


0.98 


0.95 


105-122 


51-60 


0.90 


0.94 


0.95 


0.90 


123-140 


61-70 


0.85 


0.90 


0.93 


0.85 


141-158 


71-80 


0.80 


0.87 


0.90 


0.80 


159-176 


81-90 


0.74 


0.83 


0.87 


0.74 


177-194 


91-100 


0.67 


0.79 


0.85 


0.67 


195-212 


101-120 


0.52 


0.71 


0.79 


0.52 


213-248 


121-140 


0.30 


0.61 


0.72 


0.30 


249-284 


141-160 


— 


0.50 


0.65 


— 


285-320 


161-180 


— 


0.35 


0.58 


— 


321-356 


181-200 


— 


— 


0.49 


— 


357-392 


201-225 


— 


— 


0.35 


— 


393^37 



2002 Edition 



NATIONAL ELECTRICAL CODE 



ARTICLE 310 — CONDUCTORS FOR GENERAL WIRING 



70-149 



Table 310.20 Ampacities of Not More Than Three Single Insulated Conductors, Rated Through 2000 Volts, 
Supported on a Messenger, Based on Ambient Air Temperature of 40°C (104°F) 





Temperature Rating of Conductor (See Table 310.13.) 






75°C (167°F) 


90°C (194°F) 


75°C (167°F) 


90°C (194°F) 








Types MI, THHN, 












THHW, THW-2, 




Types THHN, THHW, 






Types RHW, 


THWN-2, RfflL 




RHH, XHHW, 






THHW, THW, 


RHW-2, USE-2, 


Types RHW, THW, 


RHW-2, XHHW-2, 






THWN, XHHW, 


XHHW, XHHW-2, 


THWN, THHW, 


THW-2, THWN-2, 






ZW 


ZW-2 


XHHW 


USE-2, ZW-2 








ALUMINUM OR COPPER-CLAD 




Size AWG or kcmil 


COPPER 


ALUMINUM 


Size AWG or kcmil 


8 


57 


66 


44 


51 


8 


6 


76 


89 


59 


69 


6 


4 


101 


117 


78 


91 


4 


3 


118 


138 


92 


107 


3 ' 


2 


135 


158 


106 


123 


2 


1 


158 


185 


123 


144 


1 


1/0 


183 


214 


143 


167 


1/0 


2/0 


212 


247 


165 


193 


2/0 


3/0 


245 


287 


192 


224 


3/0 


4/0 


287 


335 


224 


262 


4/0 


250 


320 


374 


251 


292 


250 


300 


359 


419 


282 


328 


300 


350 


397 


464 


312 


364 


350 


400 


430 


503 


339 


395 


400 


500 


496 


580 


392 


458 


500 


600 


553 


647 


440 


514 


600 


700 


610 


714 


488 


570 


700 


750 


638 


747 


512 


598 


750 


800 


660 


773 


532 


622 


800 


900 


704 


826 


572 


669 


900 


1000 


748 


879 


612 


716 


1000 



CORRECTION FACTORS 



Ambient Temp. 

(°C) 


For ambient temperatures other than 40°C (104°F), multiply the allowable 
ampacities shown above by the appropriate factor shown below. 


Ambient Temp. 

(°F) 


21-25 


1.20 


1.14 


1.20 


1.14 


70-77 


26-30 


1.13 


1.10 


1.13 


1.10 


79-86 


31-35 


1.07 


1.05 


1.07 


1.05 


88-95 


36-40 


1.00 


1.00 


1.00 


1.00 


97-104 


41^15 


0.93 


0.95 


0.93 


0.95 


106-113 


46-50 


0.85 


0.89 


0.85 


0.89 


115-122 


51-55 


0.76 


0.84 


0.76 


0.84 


124-131 


56-60 


0.65 


0.77 


0.65 


0.77 


133-140 


61-70 


0.38 


0.63 


0.38 


0.63 


142-158 


71-80 


— 


0.45 


— 


0.45 


160-176 



NATIONAL ELECTRICAL CODE 



2002 Edition 



70-150 



ARTICLE 310 — CONDUCTORS FOR GENERAL WIRING 



Table 310.21 Ampacities of Bare or Covered Conductors in Free Air, Based on 40°C (104°F) Ambient, 
80°C (176°F) Total Conductor Temperature, 610 mm/sec (2 ft/sec) Wind Velocity 





Copper 


Conductors 






AAC Aluminum Conductors 

i 






Bare 




Covered 




Bare 


Covered 


AWGor 




AWGor 




AWGor 




AWGor 




kcmil 


Amperes 


kcmil 


Amperes 


kcmil 


Amperes 


kcmil 


Amperes 


8 


98 


8 


103 


8 


76 


8 


80 


6 


124 


6 


130 


6 


96 


6 


101 


4 


155 


4 


163 


4 


121 


4 


127 


2 


209 


2 


219 


2 


163 


2 


171 


1/0 


282 


1/0 


297 


1/0 


220 


1/0 


231 


2/0 


329 


2/0 


344 


2/0 


255 


2/0 


268 


3/0 


382 


3/0 


401 


3/0 


297 


3/0 


312 


4/0 


444 


4/0 


466 


4/0 


346 


4/0 


364 


250 


494 


250 


519 


266.8 


403 


266.8 


423 


300 


556 


300 


584 


336.4 


468 


336.4 


492 


500 


773 


500 


812 


397.5 


522 


397.5 


548 


750 


1000 


750 


1050 


477.0 


588 


477.0 


617 


1000 


1193 


1000 


1253 


556.5 


650 


556.5 


682 


— 


— 


— 


— 


636.0 


709 


636.0 


744 


— 


— 


— 


— 


795.0 


819 


795.0 


860 


— 


— 


— 


— 


954.0 


920 


— 


— 


— 


— 


— 


— 


1033.5 


968 


1033.5 


1017 


— 


— 


— 


— 


1272 


1103 


1272 


1201 


— 


— 


— 


— 


1590 


1267 


1590 


1381 


— 


— 


— 


— 


2000 


1454 


2000 


1527 



310.60 Conductors Rated 2001 to 35,000 Volts. 

(A) Definitions. 

Electrical Ducts. As used in Article 310, electrical ducts 
shall include any of the electrical conduits recognized in 
Chapter 3 as suitable for use underground; other raceways 
round in cross section, listed for underground use, and em- 
bedded in earth or concrete. 

Thermal Resistivity. As used in this Code, the heat trans- 
fer capability through a substance by conduction. It is the 
reciprocal of thermal conductivity and is designated Rho 
and expressed in the units °C-cm/watt. 

(B) Ampacities of Conductors Rated 2001 to 35,000 
Volts. Ampacities for solid dielectric-insulated conductors 
shall be permitted to be determined by tables or under en- 
gineering supervision, as provided in 310.60(C) and (D). 

(1) Selection of Ampacity. Where more than one calcu- 
lated or tabulated ampacity could apply for a given circuit 
length, the lowest value shall be used. 

Exception: Where two different ampacities apply to adja- 
cent portions of a circuit, the higher ampacity shall be 
permitted to be used beyond the point of transition, a dis- 
tance equal to 3.0 m (10 ft) or 10 percent of the circuit 
length figured at the higher ampacity, whichever is less. 

FPN: See 110.40 for conductor temperature limitations due 
to termination provisions. 



(C) Tables. Ampacities for conductors rated 2001 to 
35,000 volts shall be as specified in the Ampacity Tables 
310.67 through 310.86. Ampacities at ambient temperatures 
other than those shown in the tables shall be determined by 
the formula in 310.60(C)(4). 

FPN No. 1: For ampacities calculated in accordance with 
310.60(B), reference IEEE 835-1994 (IPCEA Pub. No. 
P-46-426), Standard Power Cable Ampacity Tables, and the 
references therein for availability of all factors and 
constants. 

FPN No. 2: Ampacities provided by this section do not 
take voltage drop into consideration. See 210.19(A), FPN 
No. 4, for branch circuits and 215.2(D), FPN No. 2, for 
feeders. 

(1) Grounded Shields. Ampacities shown in Tables 
310.69, 310.70, 310.81, and 310.82 are for cable with 
shields grounded at one point only. Where shields are 
grounded at more than one point, ampacities shall be ad- 
justed to take into consideration the heating due to shield 
currents. 

(2) Burial Depth of Underground Circuits. Where the 
burial depth of direct burial or electrical duct bank circuits 
is modified from the values shown in a figure or table, 
ampacities shall be permitted to be modified as indicated in 
(a) and (b). 

(a) Where burial depths are increased in part(s) of an 
electrical duct run, no decrease in ampacity of the conduc- 



2002 Edition 



NATIONAL ELECTRICAL CODE 



ARTICLE 310 — CONDUCTORS FOR GENERAL WIRING 



70-151 



tors is needed, provided the total length of parts of the duct 
run increased in depth is less than 25 percent of the total 
run length. 

(b) Where burial depths are deeper than shown in a 
specific underground ampacity table or figure, an ampacity 
derating factor of 6 percent per 300-mm ( 1 -ft) increase in 
depth for all values of rho shall be permitted. 

No rating change is needed where the burial depth is 
decreased. 



(3) Electrical Ducts in Figure 310.60. At locations where 
electrical ducts enter equipment enclosures from under- 
ground, spacing between such ducts, as shown in Figure 
310.60, shall be permitted to be reduced without requiring 
the ampacity of conductors therein to be reduced. 

(4) Ambients Not in Tables. Ampacities at ambient tem- 
peratures other than those shown in the tables shall be de- 
termined by means of the following formula: 



7 c & '. 



Detail 1 

290 mm x 290 mm 
(11.5 in. x 11.5 in.) 
Electrical duct bank 
One electrical duct 




190 mm (7.5 in.) 

Detail 2 

475 mm x 475 mm 
(19 in. x 19 in.) 
Electrical duct bank 
Three electrical ducts 
or 



*m& 



190 mm (7.5 in.) 

Detail 3 

475 mm x 675 mm 
(19 in. x27in.) 
Electrical duct bank 
Six electrical ducts 



190 mm 
(7.5 in.) 



190mm 
(7.5 in.) 



675 mm x 290 mm 
(27 in. x 11 .5 in.) 
Electrical duct bank 
Three electrical ducts 




190 mm 
(7.5 in.) 



190 mm 
(7.5 in.) 



600 mm 



Detail 5 

Buried 3 

conductor 

cable 

190 mm 190 mm 
(7.5 in.) (7.5 in.) 



(24 in.) 



Detail 6 

Buried 3 

conductor 

cables 



675 mm x 475 mm 
(27 in. x 19 in.) 
Electrical duct bank 
Six electrical ducts 



A 

Detail 7 

Buried triplexed 
cables (1 circuit) 



190 mm 190 mm 
(7.5 in.) (7.5 in.) 

K *+* H* 




£ 



Detail 9 

Buried single-conductor 
cables (1 circuit) 



600 mm 



190 mm 
(7.5 in.) 



190 mm 
(7.5 in.) 



Detail 4 

675 mm x 675 mm 
(27 in. x 27 in.) 
Electrical duct bank 
Nine electrical ducts 



600 mm 



(24 in.) 



1 



Detail 8 

Buried triplexed 
cables (2 circuits) 



(24 in.) 

Detail 10 

Buried single-conductor 
cables (2 circuits) 



190 mm 
(7.5 in.) 

-*+< H<- 



190 mm 
(7.5 in.) 



Note: Minimum burial depths to top electrical ducts or cables shall be in 
accordance with Section 300.50. Maximum depth to the top of 
electrical duct banks shall be 750 mm (30 in.) and maximum depth 
to the top of direct buried cables shall be 900 mm (36 in.). 



Legend 

F7°| Backfill 

L£ - ilJ (earth or concrete) 

O Electrical duct 

• Cable or cables 



Figure 310.60 Cable installation dimensions for use with Tables 310.77 through 310.86. 



NATIONAL ELECTRICAL CODE 



2002 Edition 



70-152 



ARTICLE 310 — CONDUCTORS FOR GENERAL WIRING 



Table 310.61 Conductor Application and Insulation 







Maximum 












Operating 


Applica- 






Trade 


Type 


Tempera- 


tion 




Outer 


Name 


Letter 


ture 


Provision 


Insulation 


Covering 


Medium 


MV-90 


90°C 


Dry or wet 


Thermo- 


Jacket, 


voltage 


MV-105* 


105°C 


locations 


plastic 


sheath, 


solid 






rated 


or 


or 


dielectric 






2001 
volts 
and 
higher 


thermo- 
setting 


armor 



*Where design conditions require maximum conductor temperatures 
above 90°C. 



Table 310.62 Thickness of Insulation for 601- to 2000- Volt 
Nonshielded Types RHH and RHW 



Conductor Size 


Column A 1 


Column B 2 










(AWG or kcmil) 


mm 


mils 


mm 


mils 


14-10 


2.03 


80 


1.52 


60 


8 


2.03 


80 


1.78 


70 


6-2 


2.41 


95 


1.78 


70 


1-2/0 


2.79 


110 


2.29 


90 


3/0-4/0 


2.79 


110 


2.29 


90 


213-500 


3.18 


125 


2.67 


105 


501-1000 


3.56 


140 


3.05 


120 



'Column A insulations are limited to natural, SBR, and butyl rubbers. 
2 Column B insulations are materials such as cross-linked polyethyl- 
ene, ethylene propylene rubber, and composites thereof. 



h =h 



(TC - TA 2 - ATD 
TC - TA 1 - ATD 



where: 

I x = ampacity from tables at ambient TA 1 
I 2 = ampacity at desired ambient TA 2 
TC = conductor temperature in degrees Celsius (°C) 
TA X = surrounding ambient from tables in degrees 

Celsius (°C) 
TA 2 = desired ambient in degrees Celsius (°C) 
ATD = dielectric loss temperature rise 

(D) Engineering Supervision. Under engineering supervi- 
sion, conductor ampacities shall be permitted to be calcu- 
lated by means of the following general formula: 



I = 



ITC -{TA + ATD) 
RDC{1 + YC)RCA 



where: 
TC = conductor temperature in °C 
TA = ambient temperature in °C 
ATD = dielectric loss temperature rise 
RDC = clc resistance of conductor at temperature TC 
YC = component ac resistance resulting from skin 
effect and proximity effect 
RCA = effective thermal resistance between conductor 
and surrounding ambient 

FPN: See Annex B for examples of formula applications. 



Table 310.63 Thickness of Insulation and Jacket for Nonshielded Solid Dielectric Insulated 
Conductors Rated 2001 to 8000 Volts 















2001- 


-5000 Volts 










5001-8000 Volts 100 Percer 






























it Insulation 




Dry Locations, Single 


Conductor 




Wet 


or Dry Locations 






Level Wet or '. 


Dry Locations 


Con- 


Without 




With Jacket 




Single Conductor 


Multi- 


Single 1 


Conductor 


Multi- 




Jacket 


















conductor 










conductor 


Size 


Insulation 


Insulation 


Jacket 


Insulation 


Jacket 


Insulation* 


Insulation 


Jacket 


Insulation* 


(AWG or 




































kcmil) 


mm 


mils 


mm 


mils 


mm 


mils 


mm 


mils 


mm 


mils 


mm 


mils 


mm 


mils 


mm 


mils 


mm mils 


8 


2.79 


110 


2.29 


90 


0.76 


30 


3.18 


125 


2.03 


80 


2.29 


90 


4.57 


180 


2.03 


80 


4.57 180 


6 


2.79 


110 


2.29 


90 


0.76 


30 


3.18 


125 


2.03 


80 


2.29 


90 


4.57 


180 


2.03 


80 


4.57 180 


4-2 


2.79 


110 


2.29 


90 


1.14 


45 


3.18 


125 


2.03 


80 


2.29 


90 


4.57 


180 


2.41 


95 


4.57 180 


1-2/0 


2.79 


110 


2.29 


90 


1.14 


45 


3.18 


125 


2.03 


80 


2.29 


90 


4.57 


180 


2.41 


95 


4.57 180 


3/0-4/0 


2.79 


110 


2.29 


90 


1.65 


65 


3.18 


125 


2.41 


95 


2.29 


90 


4.57 


180 


2.79 


110 


4.57 180 


213-500 


3.05 


120 


2.29 


90 


1.65 


65 


3.56 


140 


2.79 


110 


2.29 


90 


5.33 


210 


2.79 


no 


5.33 210 


501-750 


3.30 


130 


2.29 


90 


1.65 


65 


3.94 


155 


3.18 


125 


2.29 


90 


5.97 


235 


3.18 


125 


5.97 235 


751-1000 


3.30 


130 


2.29 


90 


1.65 


65 


3.94 


155 


3.18 


125 


2.29 


90 


6.35 


250 


3.56 


140 


6.35 250 



*Under a common overall covering such as a jacket, sheath, or armor. 



2002 Edition 



NATIONAL ELECTRICAL CODE 



ARTICLE 310 — CONDUCTORS FOR GENERAL WIRING 



70-153 



Table 310.64 Thickness of Insulation for Shielded Solid Dielectric Insulated 
Conductors Rated 2001 to 35,000 Volts 





2001- 
5000 Volts 

mm mils 


5001-8000 
Volts 


8001-15,000 
Volts 


15,001-25,000 
Volts 


25,001- 


-28,000 Volts 


28,001- 


-35,000 Volts 


Con- 
ductor 

Size 
(AWG 


100 

Percent 

Insulation 

Level 1 


133 

Percent 

Insulation 

Level 2 


100 

Percent 

Insulation 

Level 1 


133 

Percent 

Insulation 

Level 2 


100 

Percent 

Insulation 

Level 1 


133 

Percent 

Insulation 

Level 2 


100 

Percent 

Insulation 

Level 1 


133 

Percent 

Insulation 

Level 2 


100 

Percent 

Insulation 

Level 1 


133 

Percent 

Insulation 

Level 2 


or 
kcmil) 


mm mils 


mm mils 


mm mils 


mm mils 


mm mils 


mm mils 


mm mils 


mm mils 


mm mils 


mm mils 


8 2.29 90 

6-4 2.29 90 

2 2.29 90 

1 2.29 90 

1/0-2000 2.29 90 


2.92 115 
2.92 115 
2.92 115 
2.92 115 


3.56 140 
3.56 140 
3.56 140 
3.56 140 


4.45 175 
4.45 175 
4.45 175 


5.46 215 
5.46 215 
5.46 215 


6.60 260 
6.60 260 


8.76 345 
8.76 345 


7.11 280 
7.11 280 


8.76 345 
8.76 345 


8.76 345 


10.67 420 



1 100 Percent Insulation Level. Cables in this category shall be permitted to be applied where the system is provided with relay protection such that ground 
faults will be cleared as rapidly as possible but, in any case, within 1 minute. While these cables are applicable to the great majority of cable installations 
that are on grounded systems, they shall be permitted to be used also on other systems for which the application of cables is acceptable, provided the above 
clearing requirements are met in completely de-energizing the faulted section. 

2 133 Percent Insulation Level. This insulation level corresponds to that formerly designated for ungrounded systems. Cables in this category shall be 
permitted to be applied in situations where the clearing time requirements of the 100 percent level category cannot be met and yet there is adequate assurance 
that the faulted section will be de-energized in a time not exceeding 1 hour. Also, they shall be permitted to be used where additional insulation strength over 
the 100 percent level category is desirable. 



Table 310.67 Ampacities of Insulated Single Copper 
Conductor Cables Triplexed in Air Based on Conductor 
Temperatures of 90°C (194°F) and 105°C (221°F) and 
Ambient Air Temperature of 40°C (104°F) 



Table 310.68 Ampacities of Insulated Single Aluminum 
Conductor Cables Triplexed in Air Based on Conductor 
Temperatures of 90°C (194°F) and 105°C (221°F) and 
Ambient Air Temperature of 40°C (104°F) 







Temperature Rating of Conductor 
(See Table 310.61.) 




Conductor 

Size (AWG 

or kcmil) 




Temperature Rating of Conductor 
(See Table 310.61.) 






2001-5000 Volts 
Ampacity 


5001-35,000 Volts 
Ampacity 


2001-5000 Volts 
Ampacity 


5001-35,000 Volts 
Ampacity 


Conductor 

Size (AWG 

or kcmil) 


90°C 
(194°F) 

Type 
MV-90 


105°C 

(221°F) 

Type 
MV-105 


90°C 
(194°F) 

Type 
MV-90 


105°C 

(221°F) 

Type 

MV-105 


90°C 
(194°F) 

Type 
MV-90 


105°C 

(221°F) 

Type 
MV-105 


90°C 
(194°F) 

Type 
MV-90 


105°C 

(221°F) 

Type 

MV-105 


8 


65 


74 








8 


50 


57 








6 


90 


99 


100 


110 


6 


70 


77 


75 


84 


4 


120 


130 


130 


140 


4 


90 


100 


100 


110 


• 2 


160 


175 


170 


195 


2 


125 


135 


130 


150 


1 


185 


205 


195 


225 


1 


145 


160 


150 


175 


1/0 


215 


240 


225 


255 


1/0 


170 


185 


175 


200 


2/0 


250 


275 


260 


295 


2/0 


195 


215 


200 


230 


3/0 


290 


320 


300 


340 


3/0 


225 


250 


230 


265 


4/0 


335 


375 


345 


390 


4/0 


265 


290 


270 


305 


250 


375 


415 


380 


430 


250 


295 


325 


300 


335 


350 


465 


515 


470 


525 


350 


365 


405 


370 


415 


500 


580 


645 


580 


650 


500 


460 


510 


460 


515 


750 


750 


835 


730 


820 


750 


600 


665 


590 


660 


1000 


880 


980 


850 


950 


1000 


715 


800 


700 


780 



NATIONAL ELECTRICAL CODE 



2002 Edition 



70-154 



ARTICLE 310 — CONDUCTORS FOR GENERAL WIRING 



Table 310.69 Ampacities of Insulated Single Copper 
Conductor Isolated in Air Based on Conductor Temperatures 
of 90°C (194°F) and 105°C (221°F) and Ambient Air 
Temperature of 40°C (104°F) 



Table 310.71 Ampacities of an Insulated Three-Conductor 
Copper Cable Isolated in Air Based on Conductor 
Temperatures of 90°C (194°F) and 105°C (221°F) and 
Ambient Air Temperature of 40°C (104°F) 







Temperature Rating of Conductor 








Temperature Rating 


of Conductor 










(See Table 310.61.) 










(See Table 310.61.) 






2001-5000 Volts 


5001- 


-15,000 


15,001 


-35,000 


2001- 


-5000 Volts 


5001-35,000 Volts 


Con- 
ductor 


Ampacity 


Volts Ampacity 


Volts Ampacity 




Ampacity 


Ampacity 


90°C 


105°C 


90°C 


105°C 


90°C 


105°C 


90°C 


105°C 


90°C 


105°C 


Size 


(194°F) 


(221°F) 


(194°F) 


(221°F) 


(194°F) 


(221°F) 


Conductor 


(194°F) 


(221°F) 


(194°F) 


(221°F) 


(AWG or 


Type 


Type 


Type 


Type 


Type 


Type 


Size (AWG 


Type 


Type 


Type 


Type 


kcmil) 


MV-90 


MV-105 


MV-90 


MV-105 


MV-90 


MV-105 


or kcmil) 


MV-90 


MV-105 


MV-90 


MV-105 


8 


83 


93 








_ 


8 


59 


66 








6 


110 


120 


110 


125 


— 


— 


6 


79 


88 


93 


105 


4 


145 


160 


150 


165 


— 


— 


4 


105 


115 


120 


135 


2 


190 


215 


195 


215 


— 


— 


2 


140 


154 


165 


185 


1 


225 


250 


225 


250 


225 


250 


1 


160 


180 


185 


210 



1/0 


260 


290 


260 


290 


260 


290 


2/0 


300 


330 


300 


335 


300 


330 


3/0 


345 


385 


345 


385 


345 


380 


4/0 


400 


445 


400 


445 


395 


445 


250 


445 


495 


445 


495 


440 


490 


350 


550 


615 


550 


610 


545 


605 


500 


695 


775 


685 


765 


680 


755 


750 


900 


1000 


885 


990 


870 


970 



1/0 


185 


205 


215 


240 


2/0 


215 


240 


245 


275 


3/0 


250 


280 


285 


315 


4/0 


285 


320 


325 


360 



250 
350 
500 
750 
1000 



320 
395 
485 
615 
705 



355 
440 
545 
685 
790 



360 

435 
535 
670 
770 



400 
490 
600 

745 
860 



1000 


1075 


1200 


1060 


1185 


1040 


1160 


1250 


1230 


1370 


1210 


1350 


1185 


1320 


1500 


1365 


1525 


1345 


1500 


1315 


1465 


1750 


1495 


1665 


1470 


1640 


1430 


1595 


2000 


1605 


1790 


1575 


1755 


1535 


1710 



Table 310.70 Ampacities of Insulated Single Aluminum 
Conductor Isolated in Air Based on Conductor Temperatures 



Table 310.72 Ampacities of an Insulated Three-Conductor 
Aluminum Cable Isolated in Air Based on Conductor 
Temperatures of 90°C (194°F) and 105°C (221°F) and 
Ambient Air Temperature of 40°C (104°F) 



of 90°C (194°F) and 105°C (221°F) and Ambient Air 
Temperature of 40°C (104°F) 


Conductor 

Size (AWG 

or kcmil) 




Temperature Rating of Conductor 
(See Table 310.61.) 




Temperature Rating of Conductor 
(See Table 310.61.) 


2001-5000 Volts 
Ampacity 


5001-35,000 Volts 
Ampacity 


2001-5000 Volts 
Ampacity 

Con- 

ductor 90°C 105°C 


5001-15,000 
Volts Ampacity 


15,001-35,000 
Volts Ampacity 


90°C 
(194°F) 

Type 
MV-90 


105°C 

(221°F) 

Type 
MV-105 


90°C 
(194°F) 

Type 
MV-90 


105°C 

(221°F) 

Type 
MV-105 


90°C 105°C 
(194°F) (221°F) 

Type Type 
MV-90 MV-105 


90°C 105°C 
(194°F) (221°F) 

Type Type 
MV-90 MV-105 


Size (194°F) (221°F) 
(AWG or Type Type 
kcmil) MV-90 MV-105 


8 
6 
4 
2 
1 


46 
61 
81 
110 
125 


51 

68 

90 

120 

140 


72 
95 
125 
145 


80 
105 


8 64 71 
6 85 95 


87 97 
115 130 
150 170 
175 195 


175 195 


145 
165 


4 115 125 
2 150 165 
1 175 195 


1/0 
2/0 


145 
170 


160 

185 


170 
190 


185 
215 



1/0 


200 


225 


200 


225 


200 


225 


2/0 


230 


260 


235 


260 


230 


260 


3/0 


270 


300 


270 


300 


270 


300 


4/0 


310 


350 


310 


350 


310 


345 


250 


345 


385 


345 


385 


345 


380 


350 


430 


480 


430 


480 


430 


475 


500 


545 


605 


535 


600 


530 


590 


750 


710 


790 


700 


780 


685 


765 



3/0 
4/0 



195 

225 



215 
250 



220 

255 



245 
285 



250 
350 
500 
750 
1000 



250 
310 
385 
495 
585 



280 
345 
430 
550 
650 



280 
345 
425 
540 
635 



315 
385 
475 
600 
705 



1000 


855 


950 


840 


940 


825 


920 


1250 


980 


1095 


970 


1080 


950 


1055 


1500 


1105 


1230 


1085 


1215 


1060 


1180 


1750 


1215 


1355 


1195 


1335 


1165 


1300 


2000 


1320 


1475 


1295 


1445 


1265 


1410 



2002 Edition 



NATIONAL ELECTRICAL CODE 



ARTICLE 310 — CONDUCTORS FOR GENERAL WIRING 



70-155 



Table 310.73 Ampacities of an Insulated Triplexed or Three 
Single-Conductor Copper Cables in Isolated Conduit in Air 
Based on Conductor Temperatures of 90°C (194°F) and 105°C 
(221°F) and Ambient Air Temperature of 40°C (104°F) 



Table 310.75 Ampacities of an Insulated Three-Conductor 
Copper Cable in Isolated Conduit in Air Based on 
Conductor Temperatures of 90°C (194°F) and 105°C (221°F) 
and Ambient Air Temperature of 40°C (104°F) 







Temperature 


Rating of Conductor 






Temperature 


Rating of Conductor 








(See' 


Table 310.61.) 








(See Table 310.61.) 






2001- 


-5000 Volts 


5001- 


35,000 Volts 


2001- 


-5000 Volts 


5001-35,000 Volts 




Ampacity 


Ampacity 




Ampacity 


Ampacity 




90°C 


105°C 


90°C 


105°C 


90°C 


105°C 


90°C 


105°C 


Conductor 


(194°F) 


(221°F) 


(194°F) 


(221°F) 


Conductor 


(194°F) 


(221°F) 


(194°F) 


(221 °F) 


Size (AWG 


Type 


Type 


Type 


Type 


Size (AWG 


Type 


Type 


Type 


Type 


or kcmil) 


MV-90 


MV-105 


MV-90 


MV-105 


or kcmil) 


MV-90 


MV-105 


MV-90 


MV-105 


8 


55 


61 


_ 


_ 


8 


52 


58 


_ 


_ 


6 


75 


84 


83 


93 


6 


69 


77 


83 


92 


4 


97 


110 


110 


120 


4 


91 


100 


105 


120 


2 


130 


145 


150 


165 


2 


125 


135 


145 


165 


1 


155 


175 


170 


190 


1 


140 


155 


165 


185 


1/0 


180 


200 


195 


215 


1/0 


165 


185 


195 


215 


2/0 


205 


225 


225 


255 


2/0 


190 


210 


220 


245 


3/0 


240 


270 


260 


290 


3/0 


220 


245 


250 


280 


4/0 


280 


305 


295 


330 


4/0 


255 


285 


290 


320 


250 


315 


355 


330 


365 


250 


280 


315 


315 


350 


350 


385 


430 


395 


440 


350 


350 


390 


385 


430 


500 


475 


530 


480 


535 


500 


425 


475 


470 


525 


750 


600 


665 


585 


655 


750 


525 


585 


570 


635 


1000 


690 


770 


675 


755 


1000 


590 


660 


650 


725 



Table 310.74 Ampacities of an Insulated Triplexed or Three 
Single-Conductor Aluminum Cables in Isolated Conduit in 
Air Based on Conductor Temperatures of 90°C (194°F) and 
105°C (221°F) and Ambient Air Temperature of 40°C 
(104°F) 



Table 310.76 Ampacities of an Insulated Three-Conductor 
Aluminum Cable in Isolated Conduit in Air Based on 
Conductor Temperatures of 90°C (194°F) and 105°C (221°F) 
and Ambient Air Temperature of 40°C (104°F) 







Temperature Rating of Conductor 
(See Table 310.61.) 




Conductor 
Size (AWG 
or kcmil) 




Temperature Rating of Conductot 
(See Table 310.61.) 






2001-5000 Volts 
Ampacity 


5001-35,001 
Ampac 


Volts 




2001-5000 Volts 
Ampacity 


5001-35,000 Volts 
Ampacity 


ity 




90°C 
(194°F) 

Type 
MV-90 


105°C 

(221°F) 

Type 
MV-105 


90°C 
(194°F) 

Type 
MV-90 


105°C 


Conductor 
Size (AWG 


90°C 
(194°F) 

Type 
MV-90 


105°C 

(221 °F) 

Type 

MV-105 


90°C 
(194°F) 

Type 
MV-90 


105°C 

(221 °F) 

Type 

MV-105 


(221°F) 

Type 

MV-105 


or kcmil) 


8 
6 
4 
2 
1 


41 
53 
71 
96 

no 


46 
59 
79 
105 
125 


64 
84 
115 
130 





8 
6 

4 
2 
1 


43 
58 
76 
100 
120 


48 
65 
85 
115 
135 


65 
84 
115 
130 


72 
94 
130 
150 


71 
94 
125 
145 


1/0 
2/0 
3/0 
4/0 


130 
150 
170 
200 


145 
165 
190 

225 


150 
170 
195 

225 


170 
190 


1/0 
2/0 


140 
160 
190 
215 


155 
175 
210 
240 


150 
175 
200 
230 


170 
200 
225 
260 


220 
255 


3/0 
4/0 


250 
350 
500 
750 
1000 


220 
275 
340 
430 
505 


245 
305 
380 
480 
560 


250 
305 
380 
470 
550 


280 
340 
425 
520 
615 


250 
350 


250 
305 
380 
490 
580 


280 
340 
425 
545 
645 


255 
310 
385 
485 
565 


290 
350 
430 
540 
640 


500 
750 
1000 













NATIONAL ELECTRICAL CODE 



2002 Edition 



70-156 



ARTICLE 310 — CONDUCTORS FOR GENERAL WIRING 



Table 310.77 Ampacities of Three Single-Insulated Copper 
Conductors in Underground Electrical Ducts (Three 
Conductors per Electrical Duct) Based on Ambient Earth 
Temperature of 20°C (68°F), Electrical Duct Arrangement 
per Figure 310.60, 100 Percent Load Factor, Thermal 
Resistance (RHO) of 90, Conductor Temperatures of 90°C 
(194°F) and 105°C (221°F) 



Table 310.78 Ampacities of Three Single-Insulated 
Aluminum Conductors in Underground Electrical Ducts 
(Three Conductors per Electrical Duct) Based on Ambient 
Earth Temperature of 20°C (68°F), Electrical Duct 
Arrangement per Figure 310.60, 100 Percent Load Factor, 
Thermal Resistance (RHO) of 90, Conductor Temperatures 
of 90°C (194°F) and 105°C (221°F) 



Temperature Rating of Conductor 
(See Table 310.61.) 



Temperature Rating of Conductor 
(See Table 310.61.) 



2001-5000 Volts 
Ampacity 



5001-35,000 Volts 
Ampacity 



2001-5000 Volts 
Ampacity 



Conductor Size 
(AWG or kcmil) 



90°C 
(194°F) 

Type 
MV-90 



105°C 

(221°F) 

Type 
MV-105 



90°C 
(194°F) 

Type 
MV-90 



105°C 

(221°F) 

Type 
MV-105 



Conductor 

Size (AWG 

or kcmill) 



90°C 
(194°F) 

Type 
MV-90 



105°C 

(221°F) 

Type 
MV-105 



One Circuit (See Figure 
310.60, Detail 1.) 



Three Circuits (See Figure 
310.60, Detail 2.) 



One Circuit (See Figure 
310.60, Detail 1.) 



Three Circuits (See Figure 
310.60, Detail 2.) 



Six Circuits (See 
310.60, Detail 3.) 


Figun 










8 
6 
4 




48 
62 
80 


52 
67 
86 


64 

82 


68 
88 


2 
1 




105 
115 


110 
125 


105 
120 


115 
125 



Six Circuits (See Figure 
310.60, Detail 3.) 



38 
48 
62 
80 
91 



41 
52 
67 



1/0 


135 


145 


135 


145 


2/0 


150 


160 


150 


165 


3/0 


170 


185 


170 


185 


4/0 


195 


210 


190 


205 


250 


210 


225 


210 


225 


350 


250 


270 


245 


265 


500 


300 


325 


290 


310 


750 


365 


395 


350 


375 


1000 


410 


445 


390 


415 



5001-35,000 Volts 
Ampacity 



90°C 
(194°F) 

Type 
MV-90 



50 
64 
80 
90 



105°C 
(221°F) 

Type 
MV-105 



8 


64 


69 


— 


— 


8 


50 


54 








6 


85 


92 


90 


97 


6 


66 


71 


70 


75 


4 


110 


120 


115 


125 


4 


86 


93 


91 


98 


2 


145 


155 


155 


165 


2 


115 


125 


120 


130 


1 


170 


180 


175 


185 


1 


130 


140 


135 


145 


1/0 


195 


210 


200 


215 


1/0 


150 


160 


155 


165 


2/0 


220 


235 


230 


245 


2/0 


170 


185 


175 


190 


3/0 


250 


270 


260 


275 


3/0 


195 


210 


200 


215 


4/0 


290 


310 


295 


315 


4/0 


225 


245 


230 


245 


250 


320 


345 


325 


345 


250 


250 


270 


250 


270 


350 


385 


415 


390 


415 


350 


305 


325 


305 


330 


500 


470 


505 


465 


500 


500 


370 


400 


370 


400 


750 


585 


630 


565 


610 


750 


470 


505 


455 


490 


1000 


670 


720 


640 


690 


1000 


545 


590 


525 


565 



8 


56 


60 


— 


— 


8 


44 


47 


— 


— 


6 


73 


79 


77 


83 


6 


57 


61 


60 


65 


4 


95 


100 


99 


105 


4 


74 


80 


77 


83 


2 


125 


130 


130 


135 


2 


96 


105 


100 


105 


1 


140 


150 


145 


155 


1 


110 


120 


110 


120 


1/0 


160 


175 


165 


175 


1/0 


125 


135 


125 


140 


2/0 


185 


195 


185 


200 


2/0 


145 


155 


145 


155 


3/0 


210 


225 


210 


225 


3/0 


160 


175 


165 


175 


4/0 


235 


255 


240 


255 


4/0 


185 


200 


185 


200 


250 


260 


280 


260 


280 


250 


205 


220 


200 


220 


350 


315 


335 


310 


330 


350 


245 


265 


245 


260 


500 


375 


405 


370 


395 


500 


295 


320 


290 


315 


750 


460 


495 


440 


475 


750 


370 


395 


355 


385 


1000 


525 


565 


495 


535 


1000 


425 


460 


405 


440 



54 
69 
88 
99 



1/0 


105 


110 


105 


110 


2/0 


115 


125 


115 


125 


3/0 


135 


145 


130 


145 


4/0 


150 


165 


150 


160 


250 


165 


180 


165 


175 


350 


195 


210 


195 


210 


500 


240 


255 


230 


250 


750 


290 


315 


280 


305 


1000 


335 


360 


320 


345 



2002 Edition 



NATIONAL ELECTRICAL CODE 



ARTICLE 310 — CONDUCTORS FOR GENERAL WIRING 



70-157 



Table 310.79 Ampacities of Three Insulated Copper 
Conductors Cabled Within an Overall Covering 
(Three-Conductor Cable) in Underground Electrical Ducts 
(One Cable per Electrical Duct) Based on Ambient Earth 
Temperature of 20°C (68°F), Electrical Duct Arrangement 
per Figure 310.60, 100 Percent Load Factor, Thermal 
Resistance (RHO) of 90, Conductor Temperatures of 90°C 
(194°F) and 105°C (221°C) 



Table 310.80 Ampacities of Three Insulated Aluminum 
Conductors Cabled Within an Overall Covering 
(Three-Conductor Cable) in Underground Electrical Ducts 
(One Cable per Electrical Duct) Based on Ambient Earth 
Temperature of 20°C (68°F), Electrical Duct Arrangement 
per Figure 310.60, 100 Percent Load Factor, Thermal 
Resistance (RHO) of 90, Conductor Temperatures of 90°C 
(194°F) and 105°C (221°C) 





Temperature Rating 


of Conductor 




Temperature Rating of Conductor 






(See Table 310.61.) 








(See Table 310.61.) 






2001-i 


5000 Volts 


5001-35,000 Volts 


2001-i 


5000 Volts 


5001-35,000 Volts 




Ampacity 


Ampacity 




Ampacity 


Ampacity 




90°C 


105°C 


90°C 


105°C 


90°C 


105°C 


90°C 


105°C 


Conductor Size 


(194°F) 


(221°F) 


(194°F) 


(221°F) 


Conductor Size 


(194°F) 


(221 °F) 


(194°F) 


(221°F) 


(AWG or 


Type 


Type 


Type 


Type 


(AWG or 


Type 


Type 


Type 


Type 


kcmil) 


MV-90 


MV-105 


MV-90 


MV-105 


kcmil) 


MV-90 


MV-105 


MV-90 


MV-105 


One Circuit (See Figure 








One Circuit (See Figure 








310.60, Detail 1.) 










310.60, Detail 1.) 










8 


59 


64 


_ 





8 


46 


50 








6 


78 


84 


88 


95 


6 


61 


66 


69 


74 


4 


100 


110 


115 


125 


4 


80 


86 


89 


96 


2 


135 


145 


150 


160 


2 


105 


110 


115 


125 


1 


155 


165 


170 


185 


1 


120 


130 


135 


145 


1/0 


175 


190 


195 


210 


1/0 


140 


150 


150 


165 


2/0 


200 


220 


220 


235 


2/0 


160 


170 


170 


185 


3/0 


230 


250 


250 


270 


3/0 


180 


195 


195 


210 


4/0 


265 


285 


285 


305 


4/0 


205 


220 


220 


240 


250 


290 


315 


310 


335 


250 


230 


245 


245 


265 


350 


355 


380 


375 


400 


350 


280 


310 


295 


315 


500 


430 


460 


450 


485 


500 


340 


365 


355 


385 


750 


530 


570 


545 


585 


750 


425 


460 


440 


475 


1000 


600 


645 


615 


660 


1000 


495 


535 


510 


545 


Three Circuits (See Figure 








Three Circuits (See Figure 








310.60, Detail 2.) 










310.60, Detail 2.) 










8 


53 


57 








8 


41 


44 








6 


69 


74 


75 


81 


6 


54 


58 


59 


64 


4 


89 


96 


97 


105 


4 


70 


75 


75 


81 


2 


115 


125 


125 


135 


2 


90 


97 


100 


105 


1 


135 


145 


140 


155 


1 


105 


110 


110 


120 


1/0 


150 


165 


160 


175 


1/0 


120 


125 


125 


135 


2/0 


170 


185 


185 


195 


2/0 


135 


145 


140 


155 


3/0 


195 


210 


205 


220 


3/0 


155 


165 


160 


175 


4/0 


225 


240 


230 


250 


4/0 


175 


185 


180 


195 


250 


245 


265 


255 


270 


250 


190 


205 


200 


215 


350 


295 


315 


305 


325 


350 


230 


250 


240 


255 


500 


355 


380 


360 


385 


500 


280 


300 


285 


305 


750 


430 


465 


430 


465 


750 


345 


375 


350 


375 


1000 


485 


520 


485 


515 


1000 


400 


430 


400 


430 


Six Circuits (Set 


i Figure 








Six Circuits (See Figure 








310.60, Detail 3.) 








310.60, Detail 3.) 










8 


46 


50 








8 


36 


39 








6 


60 


65 


63 


68 


6 


46 


50 


49 


53 


4 


77 


83 


81 


87 


4 


60 


65 


63 


68 


2 


98 


105 


105 


110 


2 


77 


83 


80 


86 


1 


110 


120 


115 


125 


1 


87 


94 


90 


98 


1/0 


125 


135 


130 


145 


1/0 


99 


105 


105 


110 


2/0 


145 


155 


150 


160 


2/0 


110 


120 


115 


125 


3/0 


165 


175 


170 


180 


3/0 


130 


140 


130 


140 


4/0 


185 


200 


190 


200 


4/0 


145 


155 


150 


160 


250 


200 


220 


205 


220 


250 


160 


170 


160 


170 


350 


240 


270 


245 


275 


350 


190 


205 


190 


205 


500 


290 


310 


290 


305 


500 


230 


245 


230 


245 


750 


350 


375 


340 


365 


750 


280 


305 


275 


295 


1000 


390 


420 


380 


405 


1000 


320 


345 


315 


335 



NATIONAL ELECTRICAL CODE 



2002 Edition 



70-158 



ARTICLE 310 — CONDUCTORS FOR GENERAL WIRING 



Table 310.81 Ampacities of Single Insulated Copper 
Conductors Directly Buried in Earth Based on Ambient Earth 
Temperature of 20°C (68°F), Arrangement per Figure 310.60, 
100 Percent Load Factor, Thermal Resistance (RHO) of 90, 
Conductor Temperatures of 90°C (194°F) and 105°C (221°C) 



Table 310.82 Ampacities of Single Insulated Aluminum 
Conductors Directly Buried in Earth Based on Ambient Earth 
Temperature of 20°C (68°F), Arrangement per Figure 310.60, 
100 Percent Load Factor, Thermal Resistance (RHO) of 90, 
Conductor Temperatures of 90°C (194°F) and 105°C (221°F) 



Temperature Rating of Conductor 
(See Table 310.61.) 



Temperature Rating of Conductor 
(See Table 310.61) 



2001-5000 Volts 
Ampacity 



5001-35,000 Volts 
Ampacity 



2001-5000 Volts 
Ampacity 



Conductor Size 

(AWG or 

kcmil) 



90°C 
(194°F) 

Type 
MV-90 



105°C 

(221°F) 

Type 
MV-105 



90°C 
(194°F) 

Type 
MV-90 



105°C 
(221°F) 

Type 
MV-105 



Conductor Size 

(AWG or 

kcmil) 



90°C 
(194°F) 

Type 
MV-90 



105°C 

(221 °F) 

Type 
MV-105 



One Circuit, Three 
Conductors (See Figure 
310.60, Detail 9.) 



Two Circuits, Six 
Conductors (See Figure 
310.60, Detail 10.) 



One Circuit, Three 
Conductors (See Figure 
310.60, Detail 9.) 



Two Circuits, Six 
Conductors (See Figure 
310.60, Detail 10.) 



5001-35,000 Volts 
Ampacity 



90°C 
(194°F) 

Type 
MV-90 



105°C 

(221°F) 

Type 
MV-105 



8 


110 


115 






8 


85 


90 


— 


— 


6 


140 


150 


130 


140 


6 


110 


115 


100 


110 


4 


180 


195 


170 


180 


4 


140 


150 


130 


140 


2 


230 


250 


210 


225 


2 


180 


195 


165 


175 


1 


260 


280 


240 


260 


1 


205 


220 


185 


200 


1/0 


295 


320 


275 


295 


1/0 


230 


250 


215 


230 


2/0 


335 


365 


310 


335 


2/0 


265 


285 


245 


260 


3/0 


385 


415 


355 


380 


3/0 


300 


320 


275 


295 


4/0 


435 


465 


405 


435 


4/0 


340 


365 


315 


340 


250 


470 


510 


440 


475 


250 


370 


395 


345 


370 


350 


570 


615 


535 


575 


350 


445 


480 


415 


450 


500 


690 


745 


650 


700 


500 


540 


580 


510 


545 


750 


845 


910 


805 


865 


750 


665 


720 


635 


680 


1000 


980 


1055 


930 


1005 


1000 


780 


840 


740 


795 



8 


100 


110 






8 


80 


85 


— 


— 


6 


130 


140 


120 


130 


6 


100 


110 


95 


100 


4 


165 


180 


160 


170 


4 


130 


140 


125 


130 


2 


215 


230 


195 


210 


2 


165 


180 


155 


165 


1 


240 


260 


225 


240 


1 


190 


200 


175 


190 


1/0 


275 


295 


255 


275 


1/0 


215 


230 


200 


215 


2/0 


310 


335 


290 


315 


2/0 


245 


260 


225 


245 


3/0 


355 


380 


330 


355 


3/0 


275 


295 


255 


275 


4/0 


400 


430 


375 


405 


4/0 


310 


335 


290 


315 


250 


435 


470 


410 


440 


250 


340 


365 


320 


345 


350 


520 


560 


495 


530 


350 


410 


440 


385 


415 


500 


630 


680 


600 


645 


500 


495 


530 


470 


505 


750 


775 


835 


740 


795 


750 


610 


655 


580 


625 


1000 


890 


960 


855 


920 


1000 


710 


765 


680 


730 



2002 Edition 



NATIONAL ELECTRICAL CODE 



ARTICLE 310 — CONDUCTORS FOR GENERAL WIRING 



70-159 



Table 310.83 Ampacities of Three Insulated Copper 
Conductors Cabled Within an Overall Covering 
(Three-Conductor Cable), Directly Buried in Earth Based on 
Ambient Earth Temperature of 20°C (68°F), Arrangement 
per Figure 310.60, 100 Percent Load Factor, Thermal 
Resistance (RHO) of 90, Conductor Temperatures of 90°C 
(194°F) and 105°C (221°F) 



Table 310.84 Ampacities of Three Insulated Aluminum 
Conductors Cabled Within an Overall Covering 
(Three- Conductor Cable), Directly Buried in Earth Based on 
Ambient Earth Temperature of 20°C (68°F), Arrangement 
per Figure 310.60, 100 Percent Load Factor, Thermal 
Resistance (RHO) of 90, Conductor Temperatures of 90°C 
(194°F) and 105°C (221°F) 





Temperature Rating of Conductor (See Table 




Temperati 


jre Rating of Conductor (See Table 






310.61.) 








310.61.) 


1 






2001-5000 Volts 


5001-35,000 Volts 


2001-5000 Volts 


5001-35,000 Volts 




Ampacity 


Ampacity 




Ampacity 


Ampacity 




90°C 


105°C 


90°C 


105°C 


90°C 


105°C 


90°C 


105°C 




(194°F) 


(221°F) 


(194°F) 


(221°F) 


Conductor Size 


(194°F) 


(221°F) 


(194°F) 


(221 °F) 


Conductor Size 


Type 


Type 


Type 


Type 


(AWG or 


Type 


Type 


Type 


Type 


(AWG or kcmil) 


MV-90 


MV-105 


MV-90 


MV-105 


kcmil) 


MV-90 


MV-105 


MV-90 


MV-105 


One Circuit (See 


Figure 








One Circuit (See Figure 








310.60, Detail 5.) 










310.60, Detail 5.) 










8 


85 


89 





_ 


8 


65 


70 


_ 





6 


105 


115 


115 


120 


6 


80 


88 


90 


95 


4 


135 


150 


145 


155 


4 


105 


115 


115 


125 


2 


180 


190 


185 


200 


2 


140 


150 


145 


155 


1 


200 


215 


210 


225 


1 


155 


170 


165 


175 


1/0 


230 


245 


240 


255 


1/0 


180 


190 


185 


200 


2/0 


260 


280 


270 


290 


2/0 


205 


220 


210 


225 


3/0 


295 


320 


305 


330 


3/0 


230 


250 


240 


260 


4/0 


335 


360 


350 


375 


4/0 


260 


280 


270 


295 


250 


365 


395 


380 


410 


250 


285 


310 


300 


320 


350 


440 


475 


460 


495 


350 


345 


375 


360 


390 


500 


530 


570 


550 


590 


500 


420 


450 


435 


470 


750 


650 


700 


665 


720 


750 


520 


560 


540 


580 


1000 


730 


785 


750 


810 


1000 


600 


650 


620 


665 


Two Circuits (See Figure 








Two Circuits (See Figure 








310.60, Detail 6.) 










310.60, Detail 6.) 










8 


80 


84 





_ 


8 


60 


66 


_ 


_ 


6 


100 


105 


105 


115 


6 


75 


83 


80 


95 


4 


130 


140 


135 


145 


4 


100 


110 


105 


115 


2 


165 


180 


170 


185 


2 


130 


140 


135 


145 


1 


185 


200 


195 


210 


1 


145 


155 


150 


165 


1/0 


215 


230 


220 


235 


1/0 


165 


180 


170 


185 


2/0 


240 


260 


250 


270 


2/0 


190 


205 


195 


210 


3/0 


275 


295 


280 


305 


3/0 


215 


230 


220 


240 


4/0 


310 


335 


320 


345 


4/0 


245 


260 


250 


270 


250 


340 


365 


350 


375 


250 


265 


285 


275 


295 


350 


410 


440 


420 


450 


350 


320 


345 


330 


355 


500 


490 


525 


500 


535 


500 


385 


415 


395 


425 


750 


595 


640 


605 


650 


750 


480 


515 


485 


525 


1000 


665 


715 


675 


730 


1000 


550 


590 


560 


600 



NATIONAL ELECTRICAL CODE 



2002 Edition 



70-160 



ARTICLE 310 — CONDUCTORS FOR GENERAL WIRING 



Table 310.85 Ampacities of Three Triplexed Single Insulated 
Copper Conductors Directly Buried in Earth Based on 
Ambient Earth Temperature of 20°C (68°F), Arrangement 
per Figure 310.60, 100 Percent Load Factor, Thermal 
Resistance (RHO) of 90, Conductor Temperatures 90°C 
(194°F) and 105°C (221°F) 



Table 310.86 Ampacities of Three Triplexed Single Insulated 
Aluminum Conductors Directly Buried in Earth Based on 
Ambient Earth Temperature of 20° C (68°F), Arrangement 
per Figure 310.60, 100 Percent Load Factor, Thermal 
Resistance (RHO) of 90, Conductor Temperatures 90°C 
(194°F) and 105°C (221°F) 





Temperature Rating 


; of Conductor 




Temperature Rating of Conductor 






(See Table 310.61.) 








(See Table 310.61.) 






2001-5000 Volts 


5001-35,000 Volts 


2001-5000 Volts 


5001-35,000 Volts 




Ampacity 


Ampacity 




Ampacity 


Ampacity 




90°C 


105°C 


90°C 


105°C 


90°C 


105°C 


90°C 


105°C 


Conductor 


(194°F) 


(221°F) 


(194°F) 


(221°F) 


Conductor 


(194°F) 


(221°F) 


(194°F) 


(221°F) 


Size (AWG or 


Type 


Type 


Type 


Type 


Size (AWG or 


Type 


Type 


Type 


Type 


kcmil) 


MV-90 


MV-105 


MV-90 


MV-105 


kcmil) 


MV-90 


MV-105 


MV-90 


MV-105 


One Circuit, Three 








One Circuit, Three 








Conductors (See Figure 








Conductors (See ] 


Figure 








310.60, Detail 7.) 










310.60, Detail 7.) 










8 


90 


95 


_ 





8 


70 


75 








6 


120 


130 


115 


120 


6 


90 


100 


90 


95 


4 


150 


165 


150 


160 


4 


120 


130 


115 


125 


2 


195 


205 


190 


205 


2 


155 


165 


145 


155 


1 


225 


240 


215 


230 


1 


175 


190 


165 


175 


1/0 


255 


270 


245 


260 


1/0 


200 


210 


190 


205 


2/0 


290 


310 


275 


295 


2/0 


225 


240 


215 


230 


3/0 


330 


360 


315 


340 


3/0 


255 


275 


245 


265 


4/0 


375 


405 


360 


385 


4/0 


290 


310 


280 


305 


250 


410 


445 


390 


410 


250 


320 


350 


305 


325 


350 


490 


580 


470 


505 


350 


385 


420 


370 


400 


500 


590 


635 


565 


605 


500 


465 


500 


445 


480 


750 


725 


780 


685 


740 


750 


580 


625 


550 


590 


1000 


825 


885 


770 


830 


1000 


670 


725 


635 


680 


Two Circuits, Six 










Two Circuits, Six 










Conductors (See Figure 








Conductors (See ; 


Figure 








310.60, Detail 8.) 










310.60, Detail 8.) 










8 


85 


90 


_ 





8 


65 


70 








6 


110 


115 


105 


115 


6 


85 


95 


85 


90 


4 


140 


150 


140 


150 


4 


110 


120 


105 


115 


2 


180 


195 


175 


190 


2 


140 


150 


135 


145 


1 


205 


220 


200 


215 


1 


160 


170 


155 


170 


1/0 


235 


250 


225 


240 


1/0 


180 


195 


175 


190 


2/0 


265 


285 


255 


275 


2/0 


205 


220 


200 


215 


3/0 


300 


320 


290 


315 


3/0 


235 


250 


225 


245 


4/0 


340 


365 


325 


350 


4/0 


265 


285 


255 


275 


250 


370 


395 


355 


380 


250 


290 


310 


280 


300 


350 


445 


480 


425 


455 


350 


350 


375 


335 


360 


500 


535 


575 


510 


545 


500 


420 


455 


405 


435 


750 


650 


700 


615 


660 


750 


520 


560 


485 


525 


1000 


740 


795 


690 


745 


1000 


600 


645 


565 


605 



2002 Edition 



NATIONAL ELECTRICAL CODE 



ARTICLE 312 — CABINETS, CUTOUT BOXES, AND METER SOCKET ENCLOSURES 



70-161 



ARTICLE 312 

Cabinets, Cutout Boxes, and Meter 

Socket Enclosures 



312.1 Scope. This article covers the installation and con- 
struction specifications of cabinets, cutout boxes, and meter 
socket enclosures. 

I. Installation 

312.2 Damp, Wet, or Hazardous (Classified) Locations. 

(A) Damp and Wet Locations. In damp or wet locations, 
surface-type enclosures within the scope of this article shall 
be placed or equipped so as to prevent moisture or water 
from entering and accumulating within the cabinet or cut- 
out box, and shall be mounted so there is at least 6 mm ( l A 
in.) airspace between the enclosure and the wall or other 
supporting surface. Enclosures installed in wet locations 
shall be weatherproof. 

Exception: Nonmetallic enclosures shall be permitted to be 
installed without the airspace on a concrete, masonry, tile, 
or similar surface. 

FPN: For protection against corrosion, see 300.6. 

(B) Hazardous (Classified) Locations. Installations in 
hazardous (classified) locations shall conform to Articles 
500 through 517. 

312.3 Position in Wall. In walls of concrete, tile, or other 
noncombustible material, cabinets shall be installed so that 
the front edge of the cabinet is not set back of the finished 
surface more than 6 mm ( l A in.). In walls constructed of 
wood or other combustible material, cabinets shall be flush 
with the finished surface or project therefrom. 

312.5 Cabinets, Cutout Boxes, and Meter Socket En- 
closures. Conductors entering enclosures within the scope 
of this article shall be protected from abrasion and shall 
comply with 312.5(A) through (C). 

(A) Openings to Be Closed. Openings through which con- 
ductors enter shall be adequately closed. 

(B) Metal Cabinets, Cutout Boxes, and Meter Socket 
Enclosures. Where metal enclosures within the scope of 
this article are installed with open wiring or concealed 
knob-and-tube wiring, conductors shall enter through insu- 
lating bushings or, in dry locations, through flexible tubing 
extending from the last insulating support and firmly se- 
cured to the enclosure. 



(C) Cables. Where cable is used, each cable shall be se- 
cured to the cabinet, cutout box, or meter socket enclosure. 

Exception: Cables with entirely nonmetallic sheaths shall 
be permitted to enter the top of a surface -mounted enclo- 
sure through one or more nonflexible raceways not less 
than 450 mm (18 in.) or more than 3.0 m (10 ft) in length, 
provided all the following conditions are met: 

(a) Each cable is fastened within 300 mm (12 in.), mea- 
sured along the sheath, of the outer end of the raceway. 

(b) The raceway extends directly above the enclosure and 
does not penetrate a structural ceiling. 

(c) A fitting is provided on each end of the raceway to 
protect the cable(s) from abrasion and the fittings re- 
main accessible after installation. 

(d) The raceway is sealed or plugged at the outer end using 
approved means so as to prevent access to the enclo- 
sure through the raceway. 

(e) The cable sheath is continuous through the raceway 
and extends into the enclosure beyond the fitting not 
less than 6 mm ( J A in.). 

(f) The raceway is fastened at its outer end and at other 
points in accordance with the applicable article. 

(g) Where installed as conduit or tubing, the allowable 
cable fill does not exceed that permitted for complete 
conduit or tubing systems by Table 1 of Chapter 9 of 
this Code and all applicable notes thereto. 

FPN: See Table 1 in Chapter 9, including Note 9, for al- 
lowable cable fill in circular raceways. See 310.15(B)(2)(a) 
for required ampacity reductions for multiple cables in- 
stalled in a common raceway. 

312.6 Deflection of Conductors. Conductors at terminals 
or conductors entering or leaving cabinets or cutout boxes 
and the like shall comply with 312.6(A) through (C). 

Exception: Wire-bending space in enclosures for motor 
controllers with provisions for one or two wires per termi- 
nal shall comply with 430.10(B). 

(A) Width of Wiring Gutters. Conductors shall not be 
deflected within a cabinet or cutout box unless a gutter 
having a width in accordance with Table 312.6(A) is pro- 
vided. Conductors in parallel in accordance with 310.4 
shall be judged on the basis of the number of conductors in 
parallel. 

(B) Wire-Bending Space at Terminals. Wire-bending 
space at each terminal shall be provided in accordance with 
312.6(B)(1) or (2). 

(1) Conductors Not Entering or Leaving Opposite Wall. 

Table 312.6(A) shall apply where the conductor does not 
enter or leave the enclosure through the wall opposite its 
terminal. 



NATIONAL ELECTRICAL CODE 



2002 Edition 



70-162 



ARTICLE 312 — CABINETS, CUTOUT BOXES, AND METER SOCKET ENCLOSURES 



Table 312.6(A) Minimum Wire-Bending Space at Terminals and Minimum Width of Wiring Gutters 















Wires per 


Terminal 










Wire Size 
(AWG or 




1 




2 


I 




3 




4 


[ 


5 




























kcmil) 


mm 




in. 


mm 


in. 


mm 




in. 


mm 


in. 


mm 


in. 


14-10 


Not 


specified 




























8-6 


38.1 




V/2 


— 


— 


— 




— 


— 


— 


— 


— 


4-3 


50.8 




2 


— 


— 


— 




— 


— 


— 


— 


— 


2 


63.5 




2Vl 


— 


— 


— 




— 


— 


— 


— 


— 


1 


76.2 




3 


— 


— 


— 




— 


— 


— 


— 


— 


1/0-2/0 


88.9 




V-h 


127 


5 


178 




7 














3/0-4/0 


102 




4 


152 


6 


203 




8 


— 


— 


— 


— 


250 


114 




4 ] /2 


152 


6 


203 




8 


254 


10 


— 


— 


300-350 


127 




5 


203 


8 


254 




10 


305 


12 


— 


— 


400-500 


152 




6 


203 


8 


254 




10 


305 


12 


356 


14 


600-700 


203 




8 


254 


10 


305 




12 


356 


14 


406 


16 


750-900 


203 




8 


305 


12 


356 




14 


406 


16 


457 


18 


1000-1250 


254 




10 


— 


— 


— 




— 


— - 


— 


— 


— 


1500-2000 


305 




12 


— 


— 


— 




— 


— 


— 


— 


— 



Note: Bending space at terminals shall be measured in a straight line from the end of the lug or wire 
connector (in the direction that the wire leaves the terminal) to the wall, barrier, or obstruction. 



(2) Conductors Entering or Leaving Opposite Wall. 

Table 312.6(B) shall apply where the conductor does enter 
or leave the enclosure through the wall opposite its 
terminal. 

Exception No. 1: Where the distance between the wall and 
its terminal is in accordance with Table 312.6(A), a con- 
ductor shall be permitted to enter or leave an enclosure 
through the wall opposite its terminal, provided the con- 
ductor enters or leaves the enclosure where the gutter joins 
an adjacent gutter that has a width that conforms to Table 
312.6(B) for the conductor. 

Exception No. 2: A conductor not larger than 350 kcmil 
shall be permitted to enter or leave an enclosure containing 
only a meter socket(s) through the wall opposite its termi- 
nal, provided the distance between the terminal and the 
opposite wall is not less than that specified in Table 
312.6(A) and the terminal is a lay-in type where the termi- 
nal is either of the following: 

(a) Directed toward the opening in the enclosure and 
within a 45 degree angle of directly facing the enclo- 
sure wall 

(b) Directly facing the enclosure wall and offset not greater 
than 50 percent of the bending space specified in Table 
312.6(A) 

FPN: Offset is the distance measured along the enclosure 
wall from the axis of the centerline of the terminal to a line 
passing through the center of the opening in the enclosure. 

(C) Conductors 4 AWG or Larger. Installation shall com- 
ply with 300.4(F). 



312.7 Space in Enclosures. Cabinets and cutout boxes 
shall have sufficient space to accommodate all conductors 
installed in them without crowding. 

312.8 Enclosures for Switches or Overcurrent Devices. 

Enclosures for switches or overcurrent devices shall not be 
used as junction boxes, auxiliary gutters, or raceways for 
conductors feeding through or tapping off to other switches 
or overcurrent devices, unless adequate space for this pur- 
pose is provided. The conductors shall not fill the wiring 
space at any cross section to more than 40 percent of the 
cross-sectional area of the space, and the conductors, 
splices, and taps shall not fill the wiring space at any cross 
section to more than 75 percent of the cross- sectional area 
of that space. 

312.9 Side or Back Wiring Spaces or Gutters. Cabinets 
and cutout boxes shall be provided with back-wiring 
spaces, gutters, or wiring compartments as required by 
312.11(C) and(D). 

II. Construction Specifications 

312.10 Material. Cabinets, cutout boxes, and meter socket 
enclosures shall comply with 312.10(A) through (C). 

(A) Metal Cabinets and Cutout Boxes. Metal enclosures 
within the scope of this article shall be protected both in- 
side and outside against corrosion. 

FPN: For information on protection against corrosion, see 
300.6. 



2002 Edition 



NATIONAL ELECTRICAL CODE 



ARTICLE 312 — CABINETS, CUTOUT BOXES, AND METER SOCKET ENCLOSURES 



70-163 



Table 312.6(B) Minimum Wire-Bending Space at Terminals 







Wires per Terminal 


Wire Size (AWG or kcmil) 


1 


2 


3 


4 or 


More 




Compact 




















Stranded 




















AA-8000 




















Aluminum 




















Alloy 


















All Other 


Conductors 


















Conductors 


(See Note 3.) 


mm 


in. 


mm 


in. 


mm 


in. 


mm 


in. 


14-10 


12-8 


Not 


specified 


— 


— 







— 


— 


8 


6 


38.1 


V/2 


— 


— 


— 




— 


— 


6 


4 


50.8 


2 


— 


— 


— 




— 


— 


4 


2 


76.2 


3 


— 


— 


— 




— 


— 


3 


1 


76.2 


3 


— 


— 


— 




— 


— 


2 


1/0 


88.9 


3Vl 


— 


— 


— 




— 


— 


1 


2/0 


114 


AVi 


— 


— 


— 




— 


— 


1/0 


3/0 


140 


5Vi 


140 


5'/2 


178 


7 








2/0 


4/0 


152 


6 


152 


6 


190 


7'/2 


— 


— 


3/0 


250 


165 a 


6'/ 2 a 


165 a 


6V 2 a 


203 


8 


— 


— 


4/0 


300 


178 b 


7 b 


190 c 


V/2 C 


216 a 


8'/ 2 a 


— 


— 


250 


350 


216 d 


8i/ 2 d 


229 d 


%V2 A 


254 


9 b 


254 


10 


300 


400 


254 e 


10 e 


254 d 


10 d 


279 b 


ll b 


305 


12 


350 


500 


305 e 


12 e 


305 e 


12 e 


330 e 


13 e 


356 d 


14 d 


400 


600 


330 e 


13 e 


330 e 


13 e 


356 e 


14 e 


381 e 


15 e 


500 


700-750 


356 e 


14 e 


356 e 


14 e 


381 e 


15 e 


406 e 


16 e 


600 


800-900 


381 e 


15 e 


406 e 


16 e 


457 e 


18 e 


483 e 


19 e 


700 


1000 


406 e 


16 e 


457 e 


18 e 


508 e 


20 e 


559 e 


22 e 


750 


— 


432 e 


17 e 


483 e 


19 e 


559 e 


22 e 


610 e 


24 e 


800 





457 


18 


508 


20 


559 


22 


610 


24 


900 


— 


483 


19 


559 


22 


610 


24 


610 


24 


1000 


— 


508 


20 


— 


— 


— 




— 




1250 


— 


559 


22 


— 


— 


— 




— 




1500 


— 


610 


24 


— 


— 


— 




— 




1750 


— 


610 


24 


— 


— 


— 




— 




2000 


— 


610 


24 


— 


— 


— 




— 





1 . Bending space at terminals shall be measured in a straight line from the end of the lug or wire connector 
in a direction perpendicular to the enclosure wall. 

2. For removable and lay-in wire terminals intended for only one wire, bending space shall be permitted to be reduced 
by the following number of millimeters (inches): 

a 12.7 mm (Vi in.) d 50.8 mm (2 in.) 

b 25.4 mm (1 in.) e 76.2 mm (3 in.) 

c 38.1 mm (V/i in.) 

3. This column shall be permitted to determine the required wire-bending space for compact stranded aluminum conductors in sizes up 
to 1000 kcmil and manufactured using AA-8000 series electrical grade aluminum alloy conductor material in accordance with 310.14. 



(B) Strength. The design and construction of enclosures 
within the scope of this article shall be such as to secure 
ample strength and rigidity. If constructed of sheet steel, the 
metal thickness shall not be less than 1.35 mm (0.053 in.) 
uncoated. 

(C) Nonmetallic Cabinets. Nonmetallic cabinets shall be 
listed or they shall be submitted for approval prior to in- 
stallation. 



312.11 Spacing. The spacing within cabinets and cutout 
boxes shall comply with 312.11(A) through (D). 

(A) General. Spacing within cabinets and cutout boxes 
shall be sufficient to provide ample room for the distribu- 
tion of wires and cables placed in them and for a separation 
between metal parts of devices and apparatus mounted 
within them as follows. 



NATIONAL ELECTRICAL CODE 



2002 Edition 



70-164 ARTICLE 314 — OUTLET, DEVICE, PULL, AND JUNCTION BOXES; CONDUIT BODIES; FITTINGS; AND MANHOLES 



(1) Base. Other than at points of support, there shall be an 
airspace of at least 1.59 mm (0.0625 in.) between the base 
of the device and the wall of any metal cabinet or cutout 
box in which the device is mounted. 

(2) Doors. There shall be an airspace of at least 25.4 mm 
(1.00 in.) between any live metal part, including live metal 
parts of enclosed fuses, and the door. 

Exception: Where the door is lined with an approved insu- 
lating material or is of a thickness of metal not less than 
2.36 mm (0.093 in.) uncoated, the airspace shall not be less 
than 12.7 mm (0.500 in.). 

(3) Live Parts. There shall be an airspace of at least 
12.7 mm (0.500 in.) between the walls, back, gutter parti- 
tion, if of metal, or door of any cabinet or cutout box and 
the nearest exposed current-carrying part of devices 
mounted within the cabinet where the voltage does not 
exceed 250. This spacing shall be increased to at least 
25.4 mm (1.00 in.) for voltages of 251 to 600, nominal. 

Exception: Where the conditions in 312.11(A)(2), Excep- 
tion, are met, the airspace for nominal voltages from 251 to 
600 shall be permitted to be not less than 12.7 mm 
(0.500 in.). 

(B) Switch Clearance. Cabinets and cutout boxes shall be 
deep enough to allow the closing of the doors when 30- 
ampere branch-circuit panelboard switches are in any posi- 
tion, when combination cutout switches are in any position, 
or when other single-throw switches are opened as far as 
their construction permits. 

(C) Wiring Space. Cabinets and cutout boxes that con- 
tain devices or apparatus connected within the cabinet or 
box to more than eight conductors, including those of 
branch circuits, meter loops, feeder circuits, power cir- 
cuits, and similar circuits, but not including the supply 
circuit or a continuation thereof, shall have back-wiring 
spaces or one or more side-wiring spaces, side gutters, or 
wiring compartments. 

(D) Wiring Space — Enclosure. Side-wiring spaces, side 
gutters, or side-wiring compartments of cabinets and cutout 
boxes shall be made tight enclosures by means of covers, 
barriers, or partitions extending from the bases of the de- 
vices contained in the cabinet, to the door, frame, or sides 
of the cabinet. 

Exception: Side-wiring spaces, side gutters, and side- 
wiring compartments of cabinets shall not be required to be 
made tight enclosures where those side spaces contain only 
conductors that enter the cabinet directly opposite to the 
devices where they terminate. 

Partially enclosed back-wiring spaces shall be provided 
with covers to complete the enclosure. Wiring spaces that 



are required by 312.11(C) and are exposed when doors are 
open shall be provided with covers to complete the enclo- 
sure. Where adequate space is provided for feed-through 
conductors and for splices as required in 312.8, additional 
barriers shall not be required. 



:;:;-;-:;::;;;:?::-; : ;D : ;mticle '^s^^C\[' 

Outlet; Device, Pull, and Junction Boxes; 
; Conduit Bodies; Fittings; and Manholes 

I. Scope and General 

314.1 Scope. This article covers the installation and use of 
all boxes and conduit bodies used as outlet, device, junc- 
tion, or pull boxes, depending on their use, and manholes 
and other electric enclosures intended for personnel entry. 
Cast, sheet metal, nonmetallic, and other boxes such as FS, 
FD, and larger boxes are not classified as conduit bodies. 
This article also includes installation requirements for fit- 
tings used to join raceways and to connect raceways and 
cables to boxes and conduit bodies. 

314.2 Round Boxes. Round boxes shall not be used where 
conduits or connectors requiring the use of locknuts or 
bushings are to be connected to the side of the box. 

314.3 Nonmetallic Boxes. Nonmetallic boxes shall be per- 
mitted only with open wiring on insulators, concealed knob- 
and-tube wiring, cabled wiring methods with entirely nonme- 
tallic sheaths, flexible cords, and nonmetallic raceways. 

Exception No. 1: Where internal bonding means are pro- 
vided between all entries, nonmetallic boxes shall be per- 
mitted to be used with metal raceways or metal-armored 
cables. 

Exception No. 2: Where integral bonding means with a 
provision for attaching an equipment bonding jumper in- 
side the box are provided between all threaded entries in 
nonmetallic boxes listed for the purpose, nonmetallic boxes 
shall be permitted to be used with metal raceways or metal- 
armored cables. 

314.4 Metal Boxes. All metal boxes shall be grounded in 
accordance with the provisions of Article 250. 

314.5 Short-Radius Conduit Bodies. Conduit bodies such 
as capped elbows and service-entrance elbows that enclose 
conductors 6 AWG or smaller, and are only intended to 
enable the installation of the raceway and the contained 
conductors, shall not contain splices, taps, or devices and 



2002 Edition 



NATIONAL ELECTRICAL CODE 



ARTICLE 314 — OUTLET, DEVICE, PULL, AND JUNCTION BOXES; CONDUIT BODIES; FITTINGS; AND MANHOLES 70-165 



shall be of sufficient size to provide free space for all con- 
ductors enclosed in the conduit body. 

II. Installation 

314.15 Damp, Wet, or Hazardous (Classified) Locations. 

(A) Damp or Wet Locations. In damp or wet locations, 
boxes, conduit bodies, and fittings shall be placed or 
equipped so as to prevent moisture from entering or accu- 
mulating within the box, conduit body, or fitting. Boxes, 
conduit bodies, and fittings installed in wet locations shall 
be listed for use in wet locations. 

FPN No. 1: For boxes in floors, see 314.27(C). 

FPN No. 2: For protection against corrosion, see 300.6. 

(B) Hazardous (Classified) Locations. Installations in 
hazardous (classified) locations shall conform to Articles 
500 through 517. 

314.16 Number of Conductors in Outlet, Device, and 
Junction Boxes, and Conduit Bodies. Boxes and conduit 
bodies shall be of sufficient size to provide free space for 
all enclosed conductors. In no case shall the volume of the 
box, as calculated in 314.16(A), be less than the fill calcu- 
lation as calculated in 314.16(B). The minimum volume for 
conduit bodies shall be as calculated in 314.16(C). 

The provisions of this section shall not apply to termi- 
nal housings supplied with motors. 

FPN: For volume requirements of motor terminal hous- 
ings, see 430.12. 

Boxes and conduit bodies enclosing conductors 4 AWG 
or larger shall also comply with the provisions of 314.28. 

(A) Box Volume Calculations. The volume of a wiring 
enclosure (box) shall be the total volume of the assembled 
sections, and, where used, the space provided by plaster 
rings, domed covers, extension rings, and so forth, that are 
marked with their volume or are made from boxes the di- 
mensions of which are listed in Table 314.16(A). 

(1) Standard Boxes. The volumes of standard boxes that 
are not marked with their volume shall be as given in Table 
314.16(A). 

(2) Other Boxes. Boxes 1650 cm 3 (100 in. 3 ) or less, other 
than those described in Table 314.16(A), and nonmetallic 
boxes shall be durably and legibly marked by the manufac- 
turer with their volume. Boxes described in Table 
314.16(A) that have a volume larger than is designated in 
the table shall be permitted to have their volume marked as 
required by this section. 



(B) Box Fill Calculations. The volumes in paragraphs 
314.16(B)(1) through (5), as applicable, shall be added to- 
gether. No allowance shall be required for small fittings 
such as locknuts and bushings. 

(1) Conductor Fill. Each conductor that originates outside 
the box and terminates or is spliced within the box shall be 
counted once, and each conductor that passes through the 
box without splice or termination shall be counted once. 
The conductor fill shall be computed using Table 
314.16(B). A conductor, no part of which leaves the box, 
shall not be counted. 

Exception: An equipment grounding conductor or conduc- 
tors or not over four fixture wires smaller than 14 AWG, or 
both, shall be permitted to be omitted from the calculations 
where they enter a box from a domed luminaire (fixture) or 
similar canopy and terminate within that box. 

(2) Clamp Fill. Where one or more internal cable clamps, 
whether factory or field supplied, are present in the box, a 
single volume allowance in accordance with Table 
314.16(B) shall be made based on the largest conductor 
present in the box. No allowance shall be required for a 
cable connector with its clamping mechanism outside the 
box. 

(3) Support Fittings Fill. Where one or more luminaire 
(fixture) studs or hickeys are present in the box, a single 
volume allowance in accordance with Table 314.16(B) 
shall be made for each type of fitting based on the largest 
conductor present in the box. 

(4) Device or Equipment Fill. For each yoke or strap con- 
taining one or more devices or equipment, a double volume 
allowance in accordance with Table 314.16(B) shall be 
made for each yoke or strap based on the largest conductor 
connected to a device(s) or equipment supported by that 
yoke or strap. 

(5) Equipment Grounding Conductor Fill. Where one or 
more equipment grounding conductors or equipment bond- 
ing jumpers enter a box, a single volume allowance in ac- 
cordance with Table 314.16(B) shall be made based on the 
largest equipment grounding conductor or equipment bond- 
ing jumper present in the box. Where an additional set of 
equipment grounding conductors, as permitted by 
250.146(D), is present in the box, an additional volume 
allowance shall be made based on the largest equipment 
grounding conductor in the additional set. 

(C) Conduit Bodies. 

(1) General. Conduit bodies enclosing 6 AWG conductors 
or smaller, other than short-radius conduit bodies as de- 
scribed in 314.5, shall have a cross-sectional area not less 
than twice the cross-sectional area of the largest conduit or 



NATIONAL ELECTRICAL CODE 



2002 Edition 



70-166 ARTICLE 314 — OUTLET, DEVICE, PULL, AND JUNCTION BOXES; CONDUIT BODIES; FITTINGS; AND MANHOLES 



Table 314.16(A) Metal Boxes 



Box Trade Size 


Minimum 
Volume 


Maximum Number of Conductors* 


mm 


in. 




cm 3 


in. 3 


18 


16 


14 


12 


10 


8 


6 


100 x 32 
100 x 38 
100 x 54 


(4 x VA) 
(4 x VA) 
(4 x 2 l /s) 


round/octagonal 
round/octagonal 
round/octagonal 


205 

254 
353 


12.5 
15.5 
21.5 


8 

10 
14 


7 

8 

12 


6 

7 
10 


5 
6 
9 


5 
6 
8 


5 
5 
7 


2 
3 
4 


100 x 32 
100 x 38 
100 x 54 


(4 x VA) 
(4x VA) 
(4 x 2'/ 8 ) 


square 
square 
square 


295 
344 
497 


18.0 
21.0 
30.3 


12 
14 
20 


10 
12 
17 


9 
10 
15 


8 

9 

13 


7 

8 

12 


6 

7 
10 


3 
4 
6 


120 x 32 
120 x 38 
120 x 54 


(4"/l6X 11/4) 

(4 11 /iex VA) 
(4 ll /i6x2 1 / 8 ) 


square 
square 
square 


418 
484 
689 


25.5 
29.5 
42.0 


17 
19 

28 


14 
16 

24 


12 
14 

21 


11 
13 
18 


10 
11 
16 


8 

9 

14 


5 
5 
8 


75 x 50 x 38 
75 x 50 x 50 
75 x 50 x 57 
75 x 50 x 65 
75 x 50 x 70 
75 x 50 x 90 


(3 x 2 x VA) 
(3x2x2) 
(3 x 2 x 2Va) 
(3 x 2 x 2Vi) 
(3 x 2 x 2 3 / 4 ) 
(3 x 2 x 31/2) 


device 
device 
device 
device 
device 
device 


123 
164 
172 
205 
230 
295 


7.5 
10.0 
10.5 
12.5 
14.0 
18.0 


5 
6 
7 
8 
9 
12 


4 
5 
6 
7 
8 
10 


3 
5 
5 
6 
7 
9 


3 
4 
4 
5 
6 
8 


3 
4 
4 
5 
5 
7 


2 
3 
3 
4 
4 
6 


1 

2 
2 
2 
2 
3 


100 x 54 x 38 
100 x 54 x 48 
100 x 54 x 54 


(4 x 2V% x VA) 
(4 x 2Vs x VA) 
(4 x 2 l /8 x 2V 8 ) 


device 
device 
device 


169 
213 

238 


10.3 
13.0 
14.5 


6 
8 
9 


5 
7 
8 


5 
6 

7 


4 
5 
6 


4 
5 
5 


3 
4 
4 


2 
2 
2 


95 x 50 x 65 
95 x 50 x 90 


(3 3 / 4 x 2 x 2 l A) 
(3%x2x VA). 


masonry box/gang 
masonry box/gang 


230 
344 


14.0 
21.0 


9 

14 


8 
12 


7 
10 


6 
9 


5 
8 


4 
7 


2 
4 


min. 44.5 depth 
min. 60.3 depth 


FS — single cover/gang (PA) 
FD — single cover/gang (2 3 /s) 


221 
295 


13.5 
18.0 


9 
12 


7 
10 


6 
9 


6 

8 


5- 

7 


4 
6 


2 
3 


min. 44.5 depth 
min. 60.3 depth 


FS — multiple 
FD — multiple 


cover/gang (VA) 
cover/gang (2 3 /s) 


295 
395 


18.0 
24.0 


12 
16 


10 
13 


9 
12 


8 
10 


7 
9 


6 

8 


3 
4 



• 



*Where no volume allowances are required by 314.16(B)(2) through 314.16(B)(5). 



Table 314.16(B) Volume Allowance Required per Conductor 





Free Space Within Box for Each 


Size of Conductor 




Conductor 










(AWG) 


cm 3 




in. 3 


18 


24.6 




1.50 


16 


28.7 




1.75 


14 


32.8 




2.00 


12 


36.9 




2.25 


10 


41.0 




2.50 


8 


49.2 




3.00 


6 


81.9 




5.00 



tubing to which it is attached. The maximum number of 
conductors permitted shall be the maximum number per- 
mitted by Table 1 of Chapter 9 for the conduit or tubing to 
which it is attached. 



(2) With Splices, Taps, or Devices. Only those conduit 
bodies that are durably and legibly marked by the manufac- 
turer with their volume shall be permitted to contain 
splices, taps, or devices. The maximum number of conduc- 
tors shall be computed in accordance with 314.16(B). Con- 
duit bodies shall be supported in a rigid and secure manner. 

314.17 Conductors Entering Boxes, Conduit Bodies, or 
Fittings. Conductors entering boxes, conduit bodies, or fit- 
tings shall be protected from abrasion and shall comply 
with 314.17(A) through (D). 

(A) Openings to Be Closed. Openings through which con- 
ductors enter shall be adequately closed. 

(B) Metal Boxes and Conduit Bodies. Where metal boxes 
or conduit bodies are installed with open wiring or con- 
cealed knob-and-tube wiring, conductors shall enter 
through insulating bushings or, in dry locations, through 
flexible tubing extending from the last insulating support to 



2002 Edition 



NATIONAL ELECTRICAL CODE 



ARTICLE 314 — OUTLET, DEVICE, PULL, AND JUNCTION BOXES; CONDUIT BODIES; FITTINGS; AND MANHOLES 70-167 



not less than 6 mm i}A in.) inside the box and beyond any 
cable clamps. Except as provided in 300.15(C), the wiring 
shall be firmly secured to the box or conduit body. Where 
raceway or cable is installed with metal boxes or conduit 
bodies, the raceway or cable shall be secured to such boxes 
and conduit bodies. 

(C) Nonmetallic Boxes and Conduit Bodies. Nonmetallic 
boxes and conduit bodies shall be suitable for the lowest 
temperature-rated conductor entering the box. Where non- 
metallic boxes and conduit bodies are used with open wir- 
ing or concealed knob-and-tube wiring, the conductors 
shall enter the box through individual holes. Where flexible 
tubing is used to enclose the conductors, the tubing shall 
extend from the last insulating support to not less than 
6 mm ('/4 in.) inside the box and beyond any cable clamp. 
Where nonmetallic- sheathed cable or multiconductor Type 
UF cable is used, the sheath shall extend not less than 
6 mm ( l A in.) inside the box and beyond any cable clamp. 
In all instances, all permitted wiring methods shall be se- 
cured to the boxes. 

Exception: Where nonmetallic- sheathed cable or multicon- 
ductor Type UF cable is used with single gang boxes not 
larger than a nominal size 57 mm x 100 mm (2 ] A in. 
x 4 in.) mounted in walls or ceilings, and where the cable 
is fastened within 200 mm (8 in.) of the box measured along 
the sheath and where the sheath extends through a cable 
knockout not less than 6 mm ('A in.), securing the cable to 
the box shall not be required. Multiple cable entries shall 
be permitted in a single cable knockout opening. 

(D) Conductors 4 AWG or Larger. Installation shall com- 
ply with 300.4(F). 

FPN: See 110.12(A) for requirements on closing unused 
cable and raceway knockout openings. 

314.19 Boxes Enclosing Flush Devices. Boxes used to en- 
close flush devices shall be of such design that the devices 
will be completely enclosed on back and sides and substan- 
tial support for the devices will be provided. Screws for 
supporting the box shall not be used in attachment of the 
device contained therein. 

314.20 In Wall or Ceiling. In walls or ceilings with a 
surface of concrete, tile, gypsum, plaster, or other noncom- 
bustible material, boxes shall be installed so that the front 
edge of the box will not be set back of the finished surface 
more than 6 mm ( l A in.). 

In walls and ceilings constructed of wood or other com- 
bustible surface material, boxes shall be flush with the fin- 
ished surface or project therefrom. 

314.21 Repairing Plaster and Drywall or Plasterboard. 

Plaster, drywall, or plasterboard surfaces that are broken or 



incomplete shall be repaired so there will be no gaps or 
open spaces greater than 3 mm ('/s in.) at the edge of the 
box or fitting. 

314.22 Exposed Surface Extensions. Surface extensions 
from a flush-mounted box shall be made by mounting and 
mechanically securing an extension ring over the flush box. 
Equipment grounding and bonding shall be in accordance 
with Article 250. 

Exception: A surface extension shall be permitted to be 
made from the cover of a flush-mounted box where the 
cover is designed so it is unlikely to fall off or be removed 
if its securing means becomes loose. The wiring method 
shall be flexible for a length sufficient to permit removal of 
the cover and provide access to the box interior, and ar- 
ranged so that any bonding or grounding continuity is in- 
dependent of the connection between the box and cover. 

314.23 Supports. Enclosures within the scope of this ar- 
ticle shall be supported in accordance with one or more of 
the provisions in 314.23(A) through (H). 

(A) Surface Mounting. An enclosure mounted on a build- 
ing or other surface shall be rigidly and securely fastened in 
place. If the surface does not provide rigid and secure sup- 
port, additional support in accordance with other provisions 
of this section shall be provided. 

(B) Structural Mounting. An enclosure supported from a 
structural member of a building or from grade shall be 
rigidly supported either directly or by using a metal, poly- 
meric, or wood brace. 

(1) Nails and Screws. Nails and screws, where used as a 
fastening means, shall be attached by using brackets on the 
outside of the enclosure, or they shall pass through the 
interior within 6 mm { l A in.) of the back or ends of the 
enclosure. 

(2) Braces. Metal braces shall be protected against corro- 
sion and formed from metal that is not less than 0.51 mm 
(0.020 in.) thick uncoated. Wood braces shall have a cross 
section not less than nominal 25 mm x 50 mm (1 in. 
x 2 in.). Wood braces in wet locations shall be treated for 
the conditions. Polymeric braces shall be identified as being 
suitable for the use. 

(C) Mounting in Finished Surfaces. An enclosure 
mounted in a finished surface shall be rigidly secured 
thereto by clamps, anchors, or fittings identified for the 
application. 

(D) Suspended Ceilings. An enclosure mounted to struc- 
tural or supporting elements of a suspended ceiling shall be 
not more than 1650 cm 3 (100 in. 3 ) in size and shall be 



NATIONAL ELECTRICAL CODE 



2002 Edition 



70-1 ( 



ARTICLE 314 — OUTLET, DEVICE, PULL, AND JUNCTION BOXES; CONDUIT BODIES; FITTINGS; AND MANHOLES 



securely fastened in place in accordance with either (D)(1) 
or (D)(2). 

(1) Framing Members. An enclosure shall be fastened to 
the framing members by mechanical means such as bolts, 
screws, or rivets, or by the use of clips or other securing 
means identified for use with the type of ceiling framing 
member(s) and enclosure(s) employed. The framing mem- 
bers shall be adequately supported and securely fastened to 
each other and to the building structure. 

(2) Support Wires. The installation shall comply with the 
provisions of 300.11(A). The enclosure shall be secured, 
using methods identified for the purpose, to ceiling support 
wire(s), including any additional support wire(s) installed 
for that purpose. Support wire(s) used for enclosure support 
shall be fastened at each end so as to be taut within the 
ceiling cavity. 

(E) Raceway Supported Enclosure, Without Devices, 
Luminaires (Fixtures), or Lampholders. An enclosure 
that does not contain a device(s) other than splicing devices 
or support a luminaire(s) [fixture(s)], lampholder, or other 
equipment and is supported by entering raceways shall not 
exceed 1650 cm 3 (100 in. 3 ) in size. It shall have threaded 
entries or have hubs identified for the purpose. It shall be 
supported by two or more conduits threaded wrenchtight 
into the enclosure or hubs. Each conduit shall be secured 
within 900 mm (3 ft) of the enclosure, or within 450 mm 
(18 in.) of the enclosure if all conduit entries are on the 
same side. 

Exception: Rigid metal, intermediate metal, or rigid non- 
metallic conduit or electrical metallic tubing shall be per- 
mitted to support a conduit body of any size, including a 
conduit body constructed with only one conduit entry, pro- 
vided the trade size of the conduit body is not larger than 
the largest trade size of the conduit or electrical metallic 
tubing. 

(F) Raceway Supported Enclosures, with Devices, Lu- 
minaires (Fixtures), or Lampholders. An enclosure that 
contains a device(s) or supports a luminaire(s) [fixture(s)], 
lampholder, or other equipment and is supported by enter- 
ing raceways shall not exceed 1650 cm 3 (100 in. 3 ) in size. It 
shall have threaded entries or have hubs identified for the 
purpose. It shall be supported by two or more conduits 
threaded wrenchtight into the enclosure or hubs. Each con- 
duit shall be secured within 450 mm (18 in.) of the enclo- 
sure. 

Exception No. 1: Rigid metal or intermediate metal con- 
duit shall be permitted to support a conduit body of any 
size, including a conduit body constructed with only one 
conduit entry, provided the trade size of the conduit body is 
not larger than the largest trade size of the conduit. 



Exception No. 2: An unbroken length(s) of rigid or interme- 
diate metal conduit shall be permitted to support a box used 
for luminaire (fixture) or lampholder support, or to support a 
wiring enclosure that is an integral part of a luminaire (fix- 
ture) and used in lieu of a box in accordance with 300.15(B), 
where all of the following conditions are met. 

(a) The conduit is securely fastened at a point so that the 
length of conduit beyond the last point of conduit sup- 
port does not exceed 900 mm (3 ft). 

(b) The unbroken conduit length before the last point of 
conduit support is 300 mm (12 in.) or greater, and that 
portion of the conduit is securely fastened at some point 
not less than 300 mm (12 in.) from its last point of 
support. 

(c) Where accessible to unqualified persons, the luminaire 
(fixture) or lampholder, measured to its lowest point, is 
at least 2.5 m (8 ft) above grade or standing area and 
at least 900 mm (3 ft) measured horizontally to the 2.5 
m (8 ft) elevation from windows, doors, porches, fire 
escapes, or similar locations. 

(d) A luminaire (fixture) supported by a single conduit does 
not exceed 300 mm (12 in.) in any direction from the 
point of conduit entry. 

(e) The weight supported by any single conduit does not 
exceed 9 kg (20 lb). 

(f) At the luminaire (fixture) or lampholder end, the con- 
duits) is threaded wrenchtight into the box, conduit 
body, or integral wiring enclosure, or into hubs identi- 
fied for the purpose. Where a box or conduit body is 
used for support, the luminaire (fixture) shall be se- 
cured directly to the box or conduit body, or through a 
threaded conduit nipple not over 75 mm (3 in.) long. 

(G) Enclosures in Concrete or Masonry. An enclosure 
supported by embedment shall be identified as suitably pro- 
tected from corrosion and securely embedded in concrete or 
masonry. 

(H) Pendant Boxes. An enclosure supported by a pendant 
shall comply with 314.23(H)(1) or (2). 

(1) Flexible Cord. A box shall be supported from a mul- 
ticonductor cord or cable in an approved manner that pro- 
tects the conductors against strain, such as a strain-relief 
connector threaded into a box with a hub. 

(2) Conduit. A box supporting lampholders or luminaires 
(lighting fixtures), or wiring enclosures within luminaires 
(fixtures) used in lieu of boxes in accordance with 
300.15(B), shall be supported by rigid or intermediate 
metal conduit stems. For stems longer than 450 mm 
(18 in.), the stems shall be connected to the wiring system 
with flexible fittings suitable for the location. At the lumi- 
naire (fixture) end, the conduit(s) shall be threaded 
wrenchtight into the box or wiring enclosure, or into hubs 
identified for the purpose. 



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ARTICLE 3 14 — OUTLET, DEVICE, PULL, AND JUNCTION BOXES; CONDUIT BODIES; FITTINGS; AND MANHOLES 70-1 69 



Where supported by only a single conduit, the threaded 
joints shall be prevented from loosening by the use of set- 
screws or other effective means, or the luminaire (fixture), 
at any point, shall be at least 2.5 m (8 ft) above grade or 
standing area and at least 900 mm (3 ft) measured horizon- 
tally to the 2.5 m (8 ft) elevation from windows, doors, 
porches, fire escapes, or similar locations. A luminaire (fix- 
ture) supported by a single conduit shall not exceed 
300 mm (12 in.) in any horizontal direction from the point 
of conduit entry. 

314.24 Depth of Outlet Boxes. No box shall have an in- 
ternal depth of less than 12.7 mm (Vi in.). Boxes intended 
to enclose flush devices shall have an internal depth of not 
less than 23.8 mm ( 15 /i6 in.). 

314.25 Covers and Canopies. In completed installations, 
each box shall have a cover, faceplate, lampholder, or lu- 
minaire (fixture) canopy, except where the installation com- 
plies with 410.14(B). 

(A) Nonmetallic or Metal Covers and Plates. Non- 
metallic or metal covers and plates shall be permitted. 
Where metal covers or plates are used, they shall comply 
with the grounding requirements of 250.110. 

FPN: For additional grounding requirements, see 
410.18(A) for metal luminaire (fixture) canopies, and 
404.12 and 406.5(B) for metal faceplates. 

(B) Exposed Combustible Wall or Ceiling Finish. Where 
a luminaire (fixture) canopy or pan is used, any combus- 
tible wall or ceiling finish exposed between the edge of the 
canopy or pan and the outlet box shall be covered with 
noncombustible material. 

(C) Flexible Cord Pendants. Covers of outlet boxes and 
conduit bodies having holes through which flexible cord 
pendants pass shall be provided with bushings designed for 
the purpose or shall have smooth, well-rounded surfaces on 
which the cords may bear. So-called hard rubber or com- 
position bushings shall not be used. 

314.27 Outlet Boxes. 

(A) Boxes at Luminaire (Lighting Fixture) Outlets. 

Boxes used at luminaire (lighting fixture) or lampholder 
outlets shall be designed for the purpose. At every outlet 
used exclusively for lighting, the box shall be designed or 
installed so that a luminaire (lighting fixture) may be at- 
tached. 

Exception: A wall-mounted luminaire (fixture) weighing 
not more than 3 kg (6 lb) shall be permitted to be supported 
on other boxes or plaster rings that are secured to other 
boxes, provided the luminaire (fixture) or its supporting 



yoke is secured to the box with no fewer than two No. 6 or 
larger screws. 

(B) Maximum Luminaire (Fixture) Weight. Outlet boxes 
or fittings installed as required by 314.23 shall be permitted 
to support luminaires (lighting fixtures) weighing 23 kg (50 
lb) or less. A luminaire (lighting fixture) that weighs more 
than 23 kg (50 lb) shall be supported independently of the 
outlet box unless the outlet box is listed for the weight to be 
supported. 

(C) Floor Boxes. Boxes listed specifically for this applica- 
tion shall be used for receptacles located in the floor. 

Exception: Where the authority having jurisdiction judges 
them free from likely exposure to physical damage, mois- 
ture, and dirt, boxes located in elevated floors of show 
windows and similar locations shall be permitted to be 
other than those listed for floor applications. Receptacles 
and covers shall be listed as an assembly for this type of 
location. 

(D) Boxes at Ceiling-Suspended (Paddle) Fan Outlets. 

Where a box is used as the sole support of a ceiling- 
suspended (paddle) fan, the box shall be listed for the ap- 
plication and for the weight of the fan to be supported. The 
installation shall comply with 422.18. 

314.28 Pull and Junction Boxes and Conduit Bodies. 

Boxes and conduit bodies used as pull or junction boxes 
shall comply with 314.28(A) through (D). 

Exception: Terminal housings supplied with motors shall 
comply with the provisions of 430.12. 

(A) Minimum Size. For raceways containing conductors 
of 4 AWG or larger, and for cables containing conductors of 
4 AWG or larger, the minimum dimensions of pull or junc- 
tion boxes installed in a raceway or cable run shall comply 
with the following. Where an enclosure dimension is to be 
calculated based on the diameter of entering raceways, the 
diameter shall be the metric designator (trade size) ex- 
pressed in the units of measurement employed. 

(1) Straight Pulls. In straight pulls, the length of the box 
shall not be less than eight times the metric designator 
(trade size) of the largest raceway. 

(2) Angle or U Pulls. Where splices or where angle or U 
pulls are made, the distance between each raceway entry 
inside the box and the opposite wall of the box shall not be 
less than six times the metric designator (trade size) of the 
largest raceway in a row. This distance shall be increased 
for additional entries by the amount of the sum of the di- 
ameters of all other raceway entries in the same row on the 
same wall of the box. Each row shall be calculated indi- 



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70-170 ARTICLE 314 — OUTLET, DEVICE, PULL, AND JUNCTION BOXES; CONDUIT BODIES; FITTINGS; AND MANHOLES 



vidually, and the single row that provides the maximum 
distance shall be used. 

Exception: Where a raceway or cable entry is in the wall 
of a box or conduit body opposite a removable cover, the 
distance from that wall to the cover shall be permitted to 
comply with the distance required for one wire per terminal 
in Table 312.6(A). 

The distance between raceway entries enclosing the 
same conductor shall not be less than six times the metric 
designator (trade size) of the larger raceway. 

When transposing cable size into raceway size in 
314.28(A)(1) and (A)(2), the minimum metric designator 
(trade size) raceway required for the number and size of 
conductors in the cable shall be used. 

(3) Smaller Dimensions. Boxes or conduit bodies of di- 
mensions less than those required in 314.28(A)(1) and 
(A)(2) shall be permitted for installations of combinations 
of conductors that are less than the maximum conduit or 
tubing fill (of conduits or tubing being used) permitted by 
Table 1 of Chapter 9, provided the box or conduit body has 
been listed for and is permanently marked with the maxi- 
mum number and maximum size of conductors permitted. 

(B) Conductors in Pull or Junction Boxes. In pull boxes 
or junction boxes having any dimension over 1.8 m (6 ft), 
all conductors shall be cabled or racked up in an approved 
manner. 

(C) Covers. All pull boxes, junction boxes, and conduit 
bodies shall be provided with covers compatible with the 
box or conduit body construction and suitable for the con- 
ditions of use. Where metal covers are used, they shall 
comply with the grounding requirements of 250.110. An 
extension from the cover of an exposed box shall comply 
with 314.22, Exception. 

(D) Permanent Barriers. Where permanent barriers are 
installed in a box, each section shall be considered as a 
separate box. 

314.29 Boxes and Conduit Bodies to Be Accessible. 

Boxes and conduit bodies shall be installed so that the 
wiring contained in them can be rendered accessible with- 
out removing any part of the building or, in underground 
circuits, without excavating sidewalks, paving, earth, or 
other substance that is to be used to establish the finished 
grade. 

Exception: Listed boxes shall be permitted where covered 
by gravel, light aggregate, or noncohesive granulated soil 
if their location is effectively identified and accessible for 
excavation. 



III. Construction Specifications 

314.40 Metal Boxes, Conduit Bodies, and Fittings. 

(A) Corrosion Resistant. Metal boxes, conduit bodies, 
and fittings shall be corrosion resistant or shall be well- 
galvanized, enameled, or otherwise properly coated inside 
and out to prevent corrosion. 

FPN: See 300.6 for limitation in the use of boxes and fit- 
tings protected from corrosion solely by enamel. 

(B) Thickness of Metal. Sheet steel boxes not over 
1650 cm 5 (100 in. 3 ) in size shall be made from steel not 
less than 1.59 mm (0.0625 in.) thick. The wall of a mal- 
leable iron box or conduit body and a die-cast or 
permanent-mold cast aluminum, brass, bronze, or zinc box 
or conduit body shall not be less than 2.38 mm ( 3 /32 in.) 
thick. Other cast metal boxes or conduit bodies shall have a 
wall thickness not less than 3.17 mm (Vs in.). 

Exception No. 1: Listed boxes and conduit bodies shown to 
have equivalent strength and characteristics shall be per- 
mitted to be made of thinner or other metals. 

Exception No. 2: The walls of listed short radius conduit 
bodies, as covered in 314.5, shall be permitted to be made 
of thinner metal. 

(C) Metal Boxes Over 1650 cm 3 (100 in. 3 ). Metal boxes 
over 1650 cm 3 (100 in. 3 ) in size shall be constructed so as 
to be of ample strength and rigidity. If of sheet steel, the 
metal thickness shall not be less than 1.35 mm (0.053 in.) 
uncoated. 

(D) Grounding Provisions. A means shall be provided in 
each metal box for the connection of an equipment ground- 
ing conductor. The means shall be permitted to be a tapped 
hole or equivalent. 

314.41 Covers. Metal covers shall be of the same material 
as the box or conduit body with which they are used, or 
they shall be lined with firmly attached insulating material 
that is not less than 0.79 mm (V32 in.) thick, or they shall be 
listed for the purpose. Metal covers shall be the same thick- 
ness as the boxes or conduit body for which they are used, 
or they shall be listed for the purpose. Covers of porcelain 
or other approved insulating materials shall be permitted if 
of such form and thickness as to afford the required protec- 
tion and strength. 

314.42 Bushings. Covers of outlet boxes and conduit bod- 
ies having holes through which flexible cord pendants may 
pass shall be provided with approved bushings or shall 
have smooth, well-rounded surfaces on which the cord may 
bear. Where individual conductors pass through a metal 
cover, a separate hole equipped with a bushing of suitable 
insulating material shall be provided for each conductor. 



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ARTICLE 314 — OUTLET, DEVICE, PULL, AND JUNCTION BOXES; CONDUIT BODIES; FITTINGS; AND MANHOLES 70-171 



Such separate holes shall be connected by a slot as required 
by 300.20. 

314.43 Nonmetallic Boxes. Provisions for supports or 
other mounting means for nonmetallic boxes shall be out- 
side of the box, or the box shall be constructed so as to 
prevent contact between the conductors in the box and the 
supporting screws. 

314.44 Marking. All boxes and conduit bodies, covers, 
extension rings, plaster rings, and the like shall be durably 
and legibly marked with the manufacturer's name or trade- 
mark. 

IV. Manholes and Other Electric Enclosures Intended 
for Personnel Entry 

314.50 General. Electric enclosures intended for person- 
nel entry and specifically fabricated for this purpose shall 
be of sufficient size to provide safe work space about elec- 
tric equipment with live parts that is likely to require ex- 
amination, adjustment, servicing, or maintenance while en- 
ergized. They shall have sufficient size to permit ready 
installation or withdrawal of the conductors employed 
without damage to the conductors or to their insulation. 
They shall comply with the provisions of this part. 

Exception: Where electric enclosures covered by Part IV of 
this article are part of an industrial wiring system operat- 
ing under conditions of maintenance and supervision that 
ensure only qualified persons monitor and supervise the 
system, they shall be permitted to be designed and installed 
in accordance with appropriate engineering practice. If re- 
quired by the authority having jurisdiction, design docu- 
mentation shall be provided. 

314.51 Strength. Manholes, vaults, and their means of ac- 
cess shall be designed under qualified engineering supervi- 
sion and shall withstand all loads likely to be imposed on 
the structures. 

FPN: See ANSI C2-1997, National Electrical Safety Code, 
for additional information on the loading that can be ex- 
pected to bear on underground enclosures. 

314.52 Cabling Work Space. A clear work space not less 
than 900 mm (3 ft) wide shall be provided where cables are 
located on both sides, and not less than 750 mm (2Vi ft) 
where cables are only on one side. The vertical headroom 
shall not be less than 1.8 m (6 ft) unless the opening is 
within 300 mm (1 ft), measured horizontally, of the adja- 
cent interior side wall of the enclosure. 

Exception: A manhole containing only one or more of the 
following shall be permitted to have one of the horizontal 
work space dimensions reduced to 600 mm (2 ft) where the 



other horizontal clear work space is increased so the sum 
of the two dimensions is not less than 1.8 m (6 ft): 

(a) Optical fiber cables as covered in Article 770. 

(b) Power-limited fire alarm circuits supplied in accor- 
dance with 760.41. 

(c) Class 2 or Class 3 remote-control and signaling cir- 
cuits, or both, supplied in accordance with 725.41. 

314.53 Equipment Work Space. Where electric equip- 
ment with live parts that is likely to require examination, 
adjustment, servicing, or maintenance while energized is 
installed in a manhole, vault, or other enclosure designed 
for personnel access, the work space and associated re- 
quirements in 110.26 shall be met for installations operat- 
ing at 600 volts or less. Where the installation is over 600 
volts, the work space and associated requirements in 110.34 
shall be met. A manhole access cover that weighs over 45 
kg (100 lb) shall be considered as meeting the requirements 
of 110.34(C). 

314.54 Bending Space for Conductors. Bending space 
for conductors operating at 600 volts or below shall be 
provided in accordance with the requirements of 
314.28(A). Conductors operating over 600 volts shall be 
provided with bending space in accordance with 314.71(A) 
and 314.71(B), as applicable. All conductors shall be 
cabled, racked up, or arranged in an approved manner that 
provides ready and safe access for persons to enter for 
installation and maintenance. 

Exception: Where 314.71(B) applies, each row or column 
of ducts on one wall of the enclosure shall be calculated 
individually, and the single row or column that provides the 
maximum distance shall be used. 

314.55 Access to Manholes. 

(A) Dimensions. Rectangular access openings shall not be 
less than 650 mm x 550 mm (26 in. x 22 in.). Round access 
openings in a manhole shall not be less than 650 mm 
(26 in.) in diameter. 

Exception: A manhole that has a fixed ladder that does not 
obstruct the opening or that contains only one or more of 
the following shall be permitted to reduce the minimum 
cover diameter to 600 mm (2 ft): 

(a) Optical fiber cables as covered in Article 770. 

(b) Power-limited fire alarm circuits supplied in accor- 
dance with 760.41. 

(c) Class 2 or Class 3 remote-control and signaling cir- 
cuits, or both, supplied in accordance with 725.41. 

(B) Obstructions. Manhole openings shall be free of pro- 
trusions that could injure personnel or prevent ready egress. 



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70-172 ARTICLE 314 — OUTLET, DEVICE, PULL, AND JUNCTION BOXES; CONDUIT BODIES; FITTINGS; AND MANHOLES 



(C) Location. Manhole openings for personnel shall be 
located where they are not directly above electric equip- 
ment or conductors in the enclosure. Where this is not prac- 
ticable, either a protective barrier or a fixed ladder shall be 
provided. 

(D) Covers. Covers shall be over 45 kg (100 lb) or other- 
wise designed to require the use of tools to open. They shall 
be designed or restrained so they cannot fall into the man- 
hole or protrude sufficiently to contact electrical conductors 
or equipment within the manhole. 

(E) Marking. Manhole covers shall have an identifying 
mark or logo that prominently indicates their function, such 
as "electric." 

314.56 Access to Vaults and Tunnels. 

(A) Location. Access openings for personnel shall be lo- 
cated where they are not directly above electric equipment 
or conductors in the enclosure. Other openings shall be 
permitted over equipment to facilitate installation, mainte- 
nance, or replacement of equipment. 

(B) Locks. In addition to compliance with the require- 
ments of 110.34(C), if applicable, access openings for per- 
sonnel shall be arranged so that a person on the inside can 
exit when the access door is locked from the outside, or in 
the case of normally locking by padlock, the locking ar- 
rangement shall be such that the padlock can be closed on 
the locking system to prevent locking from the outside. 

314.57 Ventilation. Where manholes, tunnels, and vaults 
have communicating openings into enclosed areas used by 
the public, ventilation to open air shall be provided wher- 
ever practicable. 

314.58 Guarding. Where conductors or equipment, or 
both, could be contacted by objects falling or being pushed 
through a ventilating grating, both conductors and live parts 
shall be protected in accordance with the requirements of 
110.27(A)(2) or 110.31(B)(1), depending on the voltage. 

314.59 Fixed Ladders. Fixed ladders shall be corrosion 
resistant. 

V. Pull and Junction Boxes for Use on Systems Over 
600 Volts, Nominal 

314.70 General. Where pull and junction boxes are used 
on systems over 600 volts, the installation shall comply 
with the provisions of Part V and also with the following 
general provisions of this article: 

(1) In Part I, 314.2, 314.3, and 314.4 



(2) In Part II, 314.15; 314.17; 314.20; 314.23(A), (B), or 
(G); 314.28(B); and 314.29 

(3) In Part III, 314.40(A) and (C) and 314.41 

314.71 Size of Pull and Junction Boxes. Pull and junction 
boxes shall provide adequate space and dimensions for the 
installation of conductors, and they shall comply with the 
specific requirements of this section. 

Exception: Terminal housings supplied with motors shall 
comply with the provisions of 430.12. 

(A) For Straight Pulls. The length of the box shall not be 
less than 48 times the outside diameter, over sheath, of the 
largest shielded or lead-covered conductor or cable entering 
the box. The length shall not be less than 32 times the 
outside diameter of the largest nonshielded conductor or 
cable. 

(B) For Angle or U Pulls. 

(1) Distance to Opposite Wall. The distance between each 
cable or conductor entry inside the box and the opposite 
wall of the box shall not be less than 36 times the outside 
diameter, over sheath, of the largest cable or conductor. 
This distance shall be increased for additional entries by the 
amount of the sum of the outside diameters, over sheath, of 
all other cables or conductor entries through the same wall 
of the box. 

Exception No. 1: Where a conductor or cable entry is in 
the wall of a box opposite a removable cover, the distance 
from that wall to the cover shall be permitted to be not less 
than the bending radius for the conductors as provided in 
300.34. 

Exception No. 2: Where cables are nonshielded and not 
lead covered, the distance of 36 times the outside diameter 
shall be permitted to be reduced to 24 times the outside 
diameter. 

(2) Distance Between Entry and Exit. The distance be- 
tween a cable or conductor entry and its exit from the box 
shall not be less than 36 times the outside diameter, over 
sheath, of that cable or conductor. 

Exception: Where cables are nonshielded and not lead 
covered, the distance of 36 times the outside diameter shall 
be permitted to be reduced to 24 times the outside diameter. 

(C) Removable Sides. One or more sides of any pull box 
shall be removable. 

314.72 Construction and Installation Requirements. 

(A) Corrosion Protection. Boxes shall be made of mate- 
rial inherently resistant to corrosion or shall be suitably 



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NATIONAL ELECTRICAL CODE 



ARTICLE 320 — ARMORED CABLE: TYPE AC 



70-173 



protected, both internally and externally, by enameling, gal- 
vanizing, plating, or other means. 

(B) Passing Through Partitions. Suitable bushings, 
shields, or fittings having smooth, rounded edges shall be 
provided where conductors or cables pass through parti- 
tions and at other locations where necessary. 

(C) Complete Enclosure. Boxes shall provide a complete 
enclosure for the contained conductors or cables. 

(D) Wiring Is Accessible. Boxes shall be installed so that 
the wiring is accessible without removing any part of the 
building. Working space shall be provided in accordance 
with 110.34. 

(E) Suitable Covers. Boxes shall be closed by suitable 
covers securely fastened in place. Underground box covers 
that weigh over 45 kg (100 lb) shall be considered meeting 
this requirement. Covers for boxes shall be permanently 
marked "DANGER — HIGH VOLTAGE — KEEP OUT." 
The marking shall be on the outside of the box cover and 
shall be readily visible. Letters shall be block type and at 
least 13 mm (V2 in.) in height. 

(F) Suitable for Expected Handling. Boxes and their 
covers shall be capable of withstanding the handling to 
which they may likely be subjected. 



ARTICLE 320 

I. General 

320.1 Scope. This article covers the use, installation, and 
construction specifications for armored cable, Type AC. 

320.2 Definition. 

Armored Cable, Type AC. A fabricated assembly of insu- 
lated conductors in a flexible metallic enclosure. See 
320.100. 

II. Installation 

320.10 Uses Permitted. Where not subject to physical 
damage, Type AC cable shall be permitted as follows: 

(1) In both exposed and concealed work 

(2) In cable trays where identified for such use 

(3) In dry locations 

(4) Embedded in plaster finish on brick or other masonry, 
except in damp or wet locations 



(5) To be run or fished in the air voids of masonry block or 
tile walls where such walls are not exposed or subject 
to excessive moisture or dampness 

320.12 Uses Not Permitted. Type AC cable shall not be 
used as follows: 

(1) In theaters and similar locations, except where permit- 
ted in 518.4 

(2) In motion picture studios 

(3) In hazardous (classified) locations except where per- 
mitted in 

a. 501.4(B), Exception 

b. 502.4(B), Exception No. 1 

c. 504.20 

(4) Where exposed to corrosive fumes or vapors 

(5) In storage battery rooms 

(6) In hoistways, or on elevators or escalators, except 
where permitted in 620.21 

(7) In commercial garages where prohibited in 511.4 and 
511.7 

320.15 Exposed Work. Exposed runs of cable, except as 
provided in 300.11(A), shall closely follow the surface of 
the building finish or of running boards. Exposed runs shall 
also be permitted to be installed on the underside of joists 
where supported at each joist and located so as not to be 
subject to physical damage. 

320.17 Through or Parallel to Framing Members. Type 
AC cable shall be protected in accordance with 300.4 
where installed through or parallel to framing members. 

320.23 In Accessible Attics. Type AC cables in accessible 
attics or roof spaces shall be installed as specified in 
320.23(A) and (B). 

(A) Where Run Across the Top of Floor Joists. Where 
run across the top of floor joists, or within 2.1 m (7 ft) of 
floor or floor joists across the face of rafters or studding, in 
attics and roof spaces that are accessible, the cable shall be 
protected by substantial guard strips that are at least as high 
as the cable. Where this space is not accessible by perma- 
nent stairs or ladders, protection shall only be required 
within 1.8 m (6 ft) of the nearest edge of the scuttle hole or 
attic entrance. 

(B) Cable Installed Parallel to Framing Members. 

Where the cable is installed parallel to the sides of rafters, 
studs, or floor joists, neither guard strips nor running boards 
shall be required, and the installation shall also comply 
with 300.4(D). 

320.24 Bending Radius. Bends in Type AC cable shall be 
made so that the cable will not be damaged. The radius of 



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70-174 



ARTICLE 322 — FLAT CABLE ASSEMBLIES: TYPE FC 



the curve of the inner edge of any bend shall not be less 
than five times the diameter of the Type AC cable. 

320.30 Securing and Supporting. Type AC cable shall be 
secured by staples, cable ties, straps, hangers, or similar 
fittings designed and installed so as not to damage the cable 
at intervals not exceeding 1.4 m (4V2 ft) and within 300 mm 
(12 in.) of every outlet box, junction box, cabinet, or fitting. 

(A) Horizontal Runs Through Holes and Notches. In 

other than vertical runs, cables installed in accordance with 
300.4 shall be considered supported and secured where 
such support does not exceed 1.4-m (4V2-ft) intervals and 
the armored cable is securely fastened in place by an ap- 
proved means within 300 mm (12 in.) of each box, cabinet, 
conduit body, or other armored cable termination. 

(B) Unsupported Cables. Type AC cable shall be permit- 
ted to be unsupported where the cable: 

(1) Is fished between access points, where concealed in 
finished buildings or structures and supporting is im- 
practicable; or 

(2) Is not more than 600 mm (2 ft) in length at terminals 
where flexibility is necessary; or 

(3) Is not more than 1.8 m (6 ft) from the last point of 
support for connections within an accessible ceiling to 
luminaire(s) [(lighting fixture(s)] or equipment. 

(C) Cable Trays. Type AC cable installed in cable trays 
shall comply with 392.8(B). 

320.40 Boxes and Fittings. At all points where the armor 
of AC cable terminates, a fitting shall be provided to protect 
wires from abrasion, unless the design of the outlet boxes 
or fittings is such as to afford equivalent protection, and, in 
addition, an insulating bushing or its equivalent protection 
shall be provided between the conductors and the armor. 
The connector or clamp by which the Type AC cable is 
fastened to boxes or cabinets shall be of such design that 
the insulating bushing or its equivalent will be visible for 
inspection. Where change is made from Type AC cable to 
other cable or raceway wiring methods, a box, fitting, or 
conduit body shall be installed at junction points as re- 
quired in 300.15. 

320.80 Ampacity. The ampacity shall be determined by 
310.15. 

(A) Thermal Insulation. Armored cable installed in ther- 
mal insulation shall have conductors rated at 90°C (194°F). 
The ampacity of cable installed in these applications shall 
be that of 60°C (140°F) conductors. 

(B) Cable Tray. The ampacity of Type AC cable installed 
in cable tray shall be determined in accordance with 
392.11. 



III. Construction Specifications 

320.100 Construction. Type AC cable shall have an armor 
of flexible metal tape and shall have an internal bonding 
strip of copper or aluminum in intimate contact with the 
armor for its entire length. 

320.104 Conductors. Insulated conductors shall be of a 
type listed in Table 310.13 or those identified for use in this 
cable. In addition, the conductors shall have an overall 
moisture-resistant and fire-retardant fibrous covering. For 
Type ACT, a moisture-resistant fibrous covering shall be 
required only on the individual conductors. 

320.108 Equipment Grounding. Type AC cable shall pro- 
vide an adequate path for equipment grounding as required 
by 250.4(A)(5) or 250.4(B)(4). 

320.120 Marking. The cable shall be marked in accor- 
dance with 310.11, except that Type AC shall have ready 
identification of the manufacturer by distinctive external 
markings on the cable sheath throughout its entire length. 



Flat Cable Assemblies: Type FC 

I. General 

322.1 Scope. This article covers the use, installation, and 
construction specifications for flat cable assemblies, Type 
FC. 

322.2 Definition. 

Flat Cable Assembly, Type FC. An assembly of parallel 
conductors formed integrally with an insulating material 
web specifically designed for field installation in surface 
metal raceway. 

II. Installation 

322.10 Uses Permitted. Flat cable assemblies shall be per- 
mitted only as follows: 

(1) As branch circuits to supply suitable tap devices for 
lighting, small appliances, or small power loads. The 
rating of the branch circuit shall not exceed 30 am- 
peres. 

(2) Where installed for exposed work. 

(3) In locations where they will not be subjected to physi- 
cal damage. Where a flat cable assembly is installed 
less than 2.5 m (8 ft) above the floor or fixed working 



2002 Edition 



NATIONAL ELECTRICAL CODE 



ARTICLE 324 — FLAT CONDUCTOR CABLE: TYPE FCC 



70-175 



platform, it shall be protected by a cover identified for 
the use. 
(4) In surface metal raceways identified for the use. The 
channel portion of the surface metal raceway systems 
shall be installed as complete systems before the flat 
cable assemblies are pulled into the raceways. 

322.12 Uses Not Permitted. Flat cable assemblies shall 
not be used as follows: 

(1) Where subject to corrosive vapors unless suitable for 
the application 

(2) In hoistways or on elevators or escalators 

(3) In any hazardous (classified) location 

(4) Outdoors or in wet or damp locations unless identified 
for the use 

322.30 Securing and Supporting. The flat cable assem- 
blies shall be supported by means of their special design 
features, within the surface metal raceways. 

The surface metal raceways shall be supported as re- 
quired for the specific raceway to be installed. 

322.40 Boxes and Fittings. 

(A) Dead Ends. Each flat cable assembly dead end shall 
be terminated in an end-cap device identified for the use. 

The dead-end fitting for the enclosing surface metal 
raceway shall be identified for the use. 

(B) Luminaire (Fixture) Hangers. Luminaire (fixture) 
hangers installed with the flat cable assemblies shall be 
identified for the use. 

(C) Fittings. Fittings to be installed with flat cable assem- 
blies shall be designed and installed to prevent physical 
damage to the cable assemblies. 

(D) Extensions. All extensions from flat cable assemblies 
shall be made by approved wiring methods, within the 
junction boxes, installed at either end of the flat cable as- 
sembly runs. 

322.56 Splices and Taps. 

(A) Splices. Splices shall be made in listed junction boxes. 

(B) Taps. Taps shall be made between any phase conduc- 
tor and the grounded conductor or any other phase conduc- 
tor by means of devices and fittings identified for the use- 
Tap devices shall be rated at not less than 15 amperes, or 
more than 300 volts to ground, and they shall be color- 
coded in accordance with the requirements of 322.120(C). 

III. Construction 

322.100 Construction. Flat cable assemblies shall consist 
of two, three, four, or five conductors. 



322.104 Conductors. Flat cable assemblies shall have 
conductors of 10 AWG special stranded copper wires. 

322.112 Insulation. The entire flat cable assembly shall be 
formed to provide a suitable insulation covering all the 
conductors and using one of the materials recognized in 
Table 310.13 for general branch-circuit wiring. 

322.120 Marking. 

(A) Temperature Rating. In addition to the provisions of 
310.11, Type FC cable shall have the temperature rating 
durably marked on the surface at intervals not exceeding 
600 mm (24 in.). 

(B) Identification of Grounded Conductor. The grounded 
conductor shall be identified throughout its length by means of 
a distinctive and durable white or gray marking. 

FPN: The color gray may have been used in the past as an 
ungrounded conductor. Care should be taken when working 
on existing systems. 

(C) Terminal Block Identification. Terminal blocks iden- 
tified for the use shall have distinctive and durable mark- 
ings for color or word coding. The grounded conductor 
section shall have a white marking or other suitable desig- 
nation. The next adjacent section of the terminal block shall 
have a black marking or other suitable designation. The 
next section shall have a red marking or other suitable 
designation. The final or outer section, opposite the 
grounded conductor section of the terminal block, shall 
have a blue marking or other suitable designation. 



ARTICLE 324 
Flat Conductor Cable: Type FCC 

I. General 

324.1 Scope. This article covers a field-installed wiring 
system for branch circuits incorporating Type FCC cable 
and associated accessories as defined by the article. The 
wiring system is designed for installation under carpet 
squares. 

324.2 Definitions. 

Bottom Shield. A protective layer that is installed between 
the floor and Type FCC flat conductor cable to protect the 
cable from physical damage and may or may not be incor- 
porated as an integral part of the cable. 

Cable Connector. A connector designed to join Type FCC 
cables without using a junction box. 



NATIONAL ELECTRICAL CODE 



2002 Edition 



70-176 



ARTICLE 324 — FLAT CONDUCTOR CABLE: TYPE FCC 



FCC System. A complete wiring system for branch circuits 
that is designed for installation under carpet squares. The 
FCC system includes Type FCC cable and associated 
shielding, connectors, terminators, adapters, boxes, and re- 
ceptacles. 

Insulating End. An insulator designed to electrically insu- 
late the end of a Type FCC cable. 

Metal Shield Connections. Means of connection designed 
to electrically and mechanically connect a metal shield to 
another metal shield, to a receptacle housing or self- 
contained device, or to a transition assembly. 

Top Shield. A grounded metal shield covering under-carpet 
components of the FCC system for the purposes of provid- 
ing protection against physical damage. 

Transition Assembly. An assembly to facilitate connection 
of the FCC system to other wiring systems, incorporating 
(1) a means of electrical interconnection and (2) a suitable 
box or covering for providing electrical safety and protec- 
tion against physical damage. 

Type FCC Cable. Three or more flat copper conductors 
placed edge-to-edge and separated and enclosed within an 
insulating assembly. 

II. Installation 
324.10 Uses Permitted. 

(A) Branch Circuits. Use of FCC systems shall be permit- 
ted both for general-purpose and appliance branch circuits 
and for individual branch circuits. 

(B) Branch-Circuit Ratings. 

(1) Voltage. Voltage between ungrounded conductors shall 
not exceed 300 volts. Voltage between ungrounded conduc- 
tors and the grounded conductor shall not exceed 150 volts. 

(2) Current. General-purpose and appliance branch cir- 
cuits shall have ratings not exceeding 20 amperes. Indi- 
vidual branch circuits shall have ratings not exceeding 30 
amperes. 

(C) Floors. Use of FCC systems shall be permitted on 
hard, sound, smooth, continuous floor surfaces made of 
concrete, ceramic, or composition flooring, wood, and simi- 
lar materials. 

(D) Walls. Use of FCC systems shall be permitted on wall 
surfaces in surface metal raceways. 

(E) Damp Locations. Use of FCC systems in damp loca- 
tions shall be permitted. 



(F) Heated Floors. Materials used for floors heated in ex- 
cess of 30°C (86°F) shall be identified as suitable for use at 
these temperatures. 

(G) System Height. Any portion of an FCC system with a 
height above floor level exceeding 2.3 mm (0.090 in.) shall 
be tapered or feathered at the edges to floor level. 

(H) Coverings. Floor-mounted Type FCC cable, cable 
connectors, and insulating ends shall be covered with car- 
pet squares not larger than 914 mm (36 in.) square. Those 
carpet squares that are adhered to the floor shall be attached 
with release-type adhesives. 

(I) Corrosion Resistance. Metal components of the sys- 
tem shall be either corrosion resistant, coated with 
corrosion-resistant materials, or insulated from contact with 
corrosive substances. 

(J) Metal-Shield Connectors. Metal shields shall be con- 
nected to each other and to boxes, receptacle housings, 
self-contained devices, and transition assemblies using 
metal-shield connectors. 

324.12 Uses Not Permitted. FCC systems shall not be 
used: 

(1) Outdoors or in wet locations 

(2) Where subject to corrosive vapors 

(3) In any hazardous (classified) location 

(4) In residential, school, and hospital buildings 

324.18 Crossings. Crossings of more than two Type FCC 
cable runs shall not be permitted at any one point. Cross- 
ings of a Type FCC cable over or under a flat communica- 
tions or signal cable shall be permitted. In each case, a 
grounded layer of metal shielding shall separate the two 
cables, and crossings of more than two flat cables shall not 
be permitted at any one point. 

324.30 Securing and Supporting. All FCC system com- 
ponents shall be firmly anchored to the floor or wall using 
an adhesive or mechanical anchoring system identified for 
this use. Floors shall be prepared to ensure adherence of the 
FCC system to the floor until the carpet squares are placed. 

324.40 Boxes and Fittings. 

(A) Cable Connections and Insulating Ends. All Type 

FCC cable connections shall use connectors identified for 
their use, installed such that electrical continuity, insulation, 
and sealing against dampness and liquid spillage are pro- 
vided. All bare cable ends shall be insulated and sealed 
against dampness and liquid spillage using listed insulating 
ends. 



2002 Edition 



NATIONAL ELECTRICAL CODE 



ARTICLE 324 — FLAT CONDUCTOR CABLE: TYPE FCC 



70-177 



(B) Polarization of Connections. All receptacles and con- 
nections shall be constructed and installed so as to maintain 
proper polarization of the system. 

(C) Shields. 

(1) Top Shield. A metal top shield shall be installed over 
all floor-mounted Type FCC cable, connectors, and insulat- 
ing ends. The top shield shall completely cover all cable 
runs, corners, connectors, and ends. 

(2) Bottom Shield. A bottom shield shall be installed be- 
neath all Type FCC cable, connectors, and insulating ends. 

(D) Connection to Other Systems. Power feed, grounding 
connection, and shield system connection between the FCC 
system and other wiring systems shall be accomplished in a 
transition assembly identified for this use. 

324.42 Devices. 

(A) Receptacles. All receptacles, receptacle housings, and 
self-contained devices used with the FCC system shall be 
identified for this use and shall be connected to the Type 
FCC cable and metal shields. Connection from any ground- 
ing conductor of the Type FCC cable shall be made to the 
shield system at each receptacle. 

(B) Receptacles and Housings. Receptacle housings and 
self-contained devices designed either for floor mounting or 
for in-wall or on-wall mounting shall be permitted for use 
with the FCC system. Receptacle housings and self- 
contained devices shall incorporate means for facilitating 
entry and termination of Type FCC cable and for electri- 
cally connecting the housing or device with the metal 
shield. Receptacles and self-contained devices shall comply 
with 406.3. Power and communications outlets installed 
together in common housing shall be permitted in accor- 
dance with 800.52(A)(1)(c), Exception No. 2. 

324.56 Splices and Taps. 

(A) FCC Systems Alterations. Alterations to FCC sys- 
tems shall be permitted. New cable connectors shall be 
used at new connection points to make alterations. It shall 
be permitted to leave unused cable runs and associated 
cable connectors in place and energized. All cable ends 
shall be covered with insulating ends. 

(B) Transition Assemblies. All transition assemblies shall 
be identified for their use. Each assembly shall incorporate 
means for facilitating entry of the Type FCC cable into the 
assembly, for connecting the Type FCC cable to grounded 
conductors, and for electrically connecting the assembly to 



the metal cable shields and to equipment grounding con- 
ductors. 

324.60 Grounding. All metal shields, boxes, receptacle 
housings, and self-contained devices shall be electrically 
continuous to the equipment grounding conductor of the 
supplying branch circuit. All such electrical connections 
shall be made with connectors identified for this use. The 
electrical resistivity of such shield system shall not be more 
than that of one conductor of the Type FCC cable used in 
the installation. 

III. Construction 
324.100 Construction. 

(A) Type FCC Cable. Type FCC cable shall be listed for 
use with the FCC system and shall consist of three, four, or 
five flat copper conductors, one of which shall be an equip- 
ment grounding conductor. 

(B) Shields. 

(1) Materials and Dimensions. All top and bottom shields 
shall be of designs and materials identified for their use. 
Top shields shall be metal. Both metallic and nonmetallic 
materials shall be permitted for bottom shields. 

(2) Resistivity. Metal shields shall have cross-sectional ar- 
eas that provide for electrical resistivity of not more than 
that of one conductor of the Type FCC cable used in the 
installation. 

324.112 Insulation. The insulating material of the cable 
shall be moisture resistant and flame retardant. All insulat- 
ing materials in the FCC systems shall be identified for 
their use. 

324.120 Markings. 

(A) Cable Marking. Type FCC cable shall be clearly and 
durably marked on both sides at intervals of not more than 
610 mm (24 in.) with the information required by 
310.11(A) and with the following additional information: 

(1) Material of conductors 

(2) Maximum temperature rating 

(3) Ampacity 

(B) Conductor Identification. Conductors shall be clearly 
and durably identified on both sides throughout their length 
as specified in 310.12. 



NATIONAL ELECTRICAL CODE 



2002 Edition 



70-178 



ARTICLE 326 — INTEGRATED GAS SPACER CABLE: TYPE IGS 



I. General 

326.1 Scope. This article covers the use, installation, and 
construction specifications for integrated gas spacer cable, 
Type IGS. 

326.2 Definition. 

Integrated Gas Spacer Cable, Type IGS. A factory as- 
sembly of one or more conductors, each individually insu- 
lated and enclosed in a loose fit, nonmetallic flexible con- 
duit as an integrated gas spacer cable rated through 600 
volts. 

II. Installation 

326.10 Uses Permitted. Type IGS cable shall be permitted 
for use under ground, including direct burial in the earth, as 
the following: 

(1) Service-entrance conductors 

(2) Feeder or branch-circuit conductors 

326.12 Uses Not Permitted. Type IGS cable shall not be 
used as interior wiring or be exposed in contact with buildings. 

326.24 Bending Radius. Where the coilable nonmetallic 
conduit and cable is bent for installation purposes or is 
flexed or bent during shipment or installation, the radii of 
bends measured to the inside of the bend shall not be less 
than specified in Table 326.24. 



shall be provided for each length of the cable and conduit 
to check the gas pressure or to inject gas into the conduit. 

326.80 Ampacity. The ampacity of Type IGS cable shall 
not exceed the values shown in Table 326.80. 



Table 326.80 


Ampacity of Type 


IGS Cable 




Size (kcmi 


1) Amperes 


Size (kcmil) 


Amperes 


250 


119 


2500 


376 


500 


168 


3000 


412 


750 


206 


3250 


429 


1000 


238 


3500 


445 


1250 


266 


3750 


461 


1500 


292 


4000 


476 


1750 


344 


4250 


491 


2000 


336 


4500 


505 


2250 


357 


4750 


519 



III. Construction Specifications 

326.104 Conductors. The conductors shall be solid alumi- 
num rods, laid parallel, consisting of one to nineteen 
12.7 mm {}/% in.) diameter rods. The minimum conductor 
size shall be 250 kcmil, and the maximum size shall be 
4750 kcmil. 

326.112 Insulation. The insulation shall be dry kraft paper 
tapes and a pressurized sulfur hexafluoride gas (SF6), both 
approved for electrical use. The nominal gas pressure shall 
be 138 kPa gauge (20 pounds per square inch gauge). The 
thickness of the paper spacer shall be as specified in Table 
326.112. 

Table 326.112 Paper Spacer Thickness 



Table 326.24 Minimum Radii of Bends 








Thickness 






Size 


Minimum Radii 




Conduit J 


Size (kcmil) 


mm 


in. 




Trade Size 

2 
3 
4 


mm 

600 

900 

1150 


in. 

24 
35 
45 




Metric Designator 

53 


250-1000 
1250-4750 


1.02 
1.52 


0.040 
0.060 


78 
103 









326.26 Bends. A run of Type IGS cable between pull 
boxes or terminations shall not contain more than the 
equivalent of four quarter bends (360 degrees total), includ- 
ing those bends located immediately at the pull box or 
terminations. 

326.40 Fittings. Terminations and splices for Type IGS 
cable shall be identified as a type that is suitable for main- 
taining the gas pressure within the conduit. A valve and cap 



326.116 Conduit. The conduit shall be a medium density 
polyethylene identified as suitable for use with natural gas 
rated pipe in metric designator 53, 78, or 103 (trade size 2, 
3, or 4). The percent fill dimensions for the conduit are 
shown in Table 326.116. 

The size of the conduit permitted for each conductor 
size shall be calculated for a percent fill not to exceed those 
found in Table 1, Chapter 9. 

326.120 Marking. The cable shall be marked in accor- 
dance with 310.11(A), 310.11(B)(1), and 310.11(D). 



2002 Edition 



NATIONAL ELECTRICAL CODE 



ARTICLE 330 — METAL-CLAD CABLE: TYPE MC 



70-179 



Table 326.116 Conduit Dimensions 



• 



Conduit Size 



Actual 
Outside 
Diameter 



Actual Inside 
Diameter 



Metric Trade 
Designator Size 



in. 



53 


2 


60 


2.375 


49.46 


1.947 


78 


3 


89 


3.500 


73.30 


2.886 


103 


4 


114 


4.500 


94.23 


3.710 



I. General 

328.1 Scope. This article covers the use, installation, and 
construction specifications for medium voltage cable, Type 
MV. 

328.2 Definition. 

Medium Voltage Cable, Type MV. A single or multicon- 
ductor solid dielectric insulated cable rated 2001 volts or 
higher. 

II. Installation 

328.10 Uses Permitted. Type MV cables shall be permit- 
ted for use on power systems rated up to 35,000 volts, 
nominal, as follows: 

(1) In wet or dry locations 

(2) In raceways 

(3) In cable trays as specified in 392.3(B)(1) 

(4) Direct buried in accordance with 300.50 

(5) In messenger-supported wiring 

328.12 Uses Not Permitted. Type MV cable shall not be 
used unless identified for the use as follows: 

(1) Where exposed to direct sunlight 

(2) In cable trays 

328.80 Ampacity. The ampacity of Type MV cable shall 
be determined in accordance with 310.60. The ampacity of 
Type MV cable installed in cable tray shall be determined 
in accordance with 392.13. 



III. Construction Specifications 

328.100 Construction. Type MV cables shall have copper, 
aluminum, or copper-clad aluminum conductors and shall 
be constructed in accordance with Article 310. 



328.120 Marking. Medium voltage cable shall be marked 
as required in 310.11. 



iiitailpadfeaDle:; Type MC 



I. General 

330.1 Scope. This article covers the use, installation, and 
construction specifications of metal-clad cable, Type MC. 

330.2 Definition. 

Metal Clad Cable, Type MC. A factory assembly of one 
or more insulated circuit conductors with or without optical 
fiber members enclosed in an armor of interlocking metal 
tape, or a smooth or corrugated metallic sheath. 

II. Installation 
330.10 Uses Permitted. 

(A) General Uses. Where not subject to physical damage, 
Type MC cables shall be permitted as follows: 

(1) For services, feeders, and branch circuits 

(2) For power, lighting, control, and signal circuits 

(3) Indoors or outdoors 

(4) Where exposed or concealed 

(5) Direct buried where identified for such use 

(6) In cable tray 

(7) In any raceway 

(8) As open runs of cable 

(9) As aerial cable on a messenger 

(10) In hazardous (classified) locations as permitted in Ar- 
ticles 501, 502, 503, 504, and 505 

(11) In dry locations and embedded in plaster finish on 
brick or other masonry except in damp or wet loca- 
tions 

(12) In wet locations where any of the following condi- 
tions are met: 

a. The metallic covering is impervious to moisture. 

b. A lead sheath or moisture-impervious jacket is pro- 
vided under the metal covering. 

c. The insulated conductors under the metallic cover- 
ing are listed for use in wet locations. 

(13) Where single-conductor cables are used, all phase 
conductors and, where used, the neutral conductor 
shall be grouped together to minimize induced voltage 
on the sheath. 

(B) Specific Uses. Type MC cable shall be installed in 
compliance with Articles 300, 490, 725, and 770.52 as ap- 



NATIONAL ELECTRICAL CODE 



2002 Edition 



70-180 



ARTICLE 330 — METAL-CLAD CABLE: TYPE MC 



plicable and in accordance with 330.10(B)(1) through 
(B)(4). 

(1) Cable Tray. Type MC cable installed in cable tray shall 
comply with Article 392. 

(2) Direct Buried. Direct-buried cable shall comply with 
300.5 or 300.50, as appropriate. 

(3) Installed as Service-Entrance Cable. Type MC cable 
installed as service-entrance cable shall comply with Ar- 
ticle 230. 

(4) Installed Outside of Buildings or as Aerial Cable. 

Type MC cable installed outside of buildings or as aerial 
cable shall comply with Article 225 and Article 396. 

330.12 Uses Not Permitted. Type MC cable shall not be 
used where exposed to the following destructive corrosive 
conditions, unless the metallic sheath is suitable for the 
conditions or is protected by material suitable for the con- 
ditions: 

(1) Direct burial in the earth 

(2) In concrete 

(3) Where exposed to cinder fills, strong chlorides, caustic 
alkalis, or vapors of chlorine or of hydrochloric acids 

330.17 Through or Parallel to Framing Members. Type 
MC cable shall be protected in accordance with 300.4 
where installed through or parallel to framing members. 

330.23 In Accessible Attics. The installation of Type MC 
cable in accessible attics or roof spaces shall also comply 
with 320.23. 

330.24 Bending Radius. Bends in Type MC cable shall be 
made so that the cable will not be damaged. The radius of 
the curve of the inner edge of any bend shall not be less 
than shown in 330.24(A) through (C). 

(A) Smooth Sheath. 

(1) Ten times the external diameter of the metallic sheath 
for cable not more than 19 mm ( 3 A in.) in external 
diameter 

(2) Twelve times the external diameter of the metallic 
sheath for cable more than 19 mm ( 3 A in.) but not more 
than 38 mm (IV2 in.) in external diameter 

(3) Fifteen times the external diameter of the metallic 
sheath for cable more than 38 mm (IV2 in.) in external 
diameter 

(B) Interlocked-Type Armor or Corrugated Sheath. 

Seven times the external diameter of the metallic sheath. 



(C) Shielded Conductors. Twelve times the overall diam- 
eter of one of the individual conductors or seven times the 
overall diameter of the multiconductor cable, whichever is 
greater. 

330.30 Securing and Supporting. Type MC cable shall be 
supported and secured at intervals not exceeding 1.8 m 
(6 ft). 

(A) Horizontal Runs Through Holes and Notches. In 

other than vertical runs, cables installed in accordance with 

300.4 shall be considered supported and secured where 
such support does not exceed 1.8-m (6-ft) intervals. 

(B) Unsupported Cables. Type MC cable shall be permit- 
ted to be unsupported where the cable: 

(1) Is fished between access points, where concealed in 
finished buildings or structures and supporting is im- 
practicable 

(2) Is not more than 1.8 m (6 ft) from the last point of 
support for connections within an accessible ceiling to 
luminaire(s) [lighting fixture(s)] or equipment 

(C) At Terminations. Cables containing four or fewer 
conductors, sized no larger than 10 AWG, shall be secured 
within 300 mm (12 in.) of every box, cabinet, fitting, or 
other cable termination. 

330.31 Single Conductors. Where single-conductor cables 
with a nonferrous armor or sheath are used, the installation 
shall comply with 300.20. 

330.40 Boxes and Fitting. Fittings used for connecting 
Type MC cable to boxes, cabinets, or other equipment shall 
be listed and identified for such use. 

330.80 Ampacity. The ampacity of Type MC cable shall 
be determined in accordance with 310.15 or 310.60 for 14 
AWG and larger conductors and in accordance with Table 

402.5 for 18 AWG and 16 AWG conductors. The installa- 
tion shall not exceed the temperature ratings of termina- 
tions and equipment. 

(A) Type MC Cable Installed in Cable Tray. The am- 
pacities for Type MC cable installed in cable tray shall be 
determined in accordance with 392.11 and 392.13. 

(B) Single Type MC Conductors Grouped Together. 

Where single Type MC conductors are grouped together in 
a triangular or square configuration and installed on a mes- 
senger or as open runs with a maintained free airspace of 
not less than 2.15 times one conductor diameter (2.15 x 
O.D.) of the largest conductor contained within the con- 
figuration and adjacent conductor configurations or cables, 



2002 Edition 



NATIONAL ELECTRICAL CODE 



ARTICLE 332 — MINERAL-INSULATED, METAL-SHEATHED CABLE: TYPE MI 



70-181 



the ampacity of the conductors shall not exceed the allow- 
able ampacities of: 

(1) Table 310.20 for conductors rated through 2000 volts 

(2) Tables 310.67 and 310.68 for conductors rated over 
2000 volts 



III. Construction Specifications 

330.104 Conductors. The conductors shall be of copper, 
aluminum, or copper-clad aluminum, solid or stranded. The 
minimum conductor size shall be 18 AWG copper and 12 
AWG aluminum or copper-clad aluminum. 

330.108 Equipment Grounding. Type MC cable shall 
provide an adequate path for equipment grounding as re- 
quired by Article 250. 

330.112 Insulation. The insulated conductors shall comply 
with 330.112(A) or (B). 

(A) 600 Volts. Insulated conductors in sizes 18 AWG and 
16 AWG shall be of a type listed in Table 402.3, with a 
maximum operating temperature not less than 90°C 
(194°F) and as permitted by 725.27. Conductors larger than 
16 AWG shall be of a type listed in Table 310.13 or of a 
type identified for use in Type MC cable. 

(B) Over 600 Volts. Insulated conductors shall be of a type 
listed in Tables 310.61 through 310.64. 

330.116 Sheath. The metallic covering shall be one of the 
following types: smooth metallic sheath, corrugated metal- 
lic sheath, interlocking metal tape armor. The metallic 
sheath shall be continuous and close fitting. A nonmagnetic 
sheath or armor shall be used on single conductor Type 
MC. Supplemental protection of an outer covering of 
corrosion-resistant material shall be permitted and shall be 
required where such protection is needed. The sheath shall 
not be used as a current-carrying conductor. 

FPN: See 300.6 for protection against corrosion. 



ARTICLE 332 
Cable: Type MI 

I. General 

332.1 Scope. This article covers the use, installation, and 
construction specifications for mineral-insulated, metal- 
sheathed cable, Type MI. 



332.2 Definition. 

Mineral-Insulated, Metal-Sheathed Cable, Type MI. A 

factory assembly of one or more conductors insulated with 
a highly compressed refractory mineral insulation and en- 
closed in a liquidtight and gastight continuous copper or 
alloy steel sheath. 

II. Installation 

332.10 Uses Permitted. Type MI cable shall be permitted 
as follows: 

(1) For services, feeders, and branch circuits 

(2) For power, lighting, control, and signal circuits 

(3) In dry, wet, or continuously moist locations 

(4) Indoors or outdoors 

(5) Where exposed or concealed 

(6) Embedded in plaster, concrete, fill, or other masonry, 
whether above or below grade 

(7) In any hazardous (classified) location 

(8) Where exposed to oil and gasoline 

(9) Where exposed to corrosive conditions not deteriorat- 
ing to its sheath 

(10) In underground runs where suitably protected against 
physical damage and corrosive conditions 

332.12 Uses Not Permitted. Type MI cable shall not be 
used where exposed to conditions that are destructive and 
corrosive to the metallic sheath unless additionally pro- 
tected by materials suitable for the conditions. 

332.17 Through or Parallel to Framing Members. Type 
MI cable shall be protected in accordance with 300.4 where 
installed through or parallel to framing members. 

332.24 Bending Radius. Bends in Type MI cable shall be 
made so that the cable will not be damaged. The radius of 
the inner edge of any bend shall not be less than shown as 
follows: 

(1) Five times the external diameter of the metallic sheath 
for cable not more than 19 mm ( 3 A in.) in external 
diameter 

(2) Ten times the external diameter of the metallic sheath 
for cable greater than 19 mm ( 3 A in.) but not more than 
25 mm (1 in.) in external diameter 

332.30 Securing and Supporting. Type MI cable shall be 
supported securely at intervals not exceeding 1.8 m (6 ft) 
by straps, staples, hangers, or similar fittings designed and 
installed so as not to damage the cable. 

(A) Horizontal Runs Through Holes and Notches. In 

other than vertical runs, cables installed in accordance with 



NATIONAL ELECTRICAL CODE 



2002 Edition 



70-182 



ARTICLE 334 — NONMETALLIC-SHEATHED CABLE: TYPES NM, NMC, AND NMS 



300.4 shall be considered supported and secured where 
such support does not exceed 1.8-m (6-ft) intervals. 

(B) Unsupported Cable. Type MI cable shall be permitted 
to be unsupported where the cable is fished. 

(C) Cable Trays. Type MI cable installed in cable trays 
shall comply with 392.8(B). 

332.31 Single Conductors. Where single-conductor cables 
are used, all phase conductors and, where used, the neutral 
conductor shall be grouped together to minimize induced 
voltage on the sheath. 



equipment grounding purposes. Where made of steel, an 
equipment grounding conductor shall be provided. 

332.112 Insulation. The conductor insulation in Type MI 
cable shall be a highly compressed refractory mineral that 
provides proper spacing for all conductors. 

332.116 Sheath. The outer sheath shall be of a continuous 
construction to provide mechanical protection and moisture 
seal. 



332.40 Boxes and Fittings. 

(A) Fittings. Fittings used for connecting Type MI cable to 
boxes, cabinets, or other equipment shall be identified for 
such use. 

(B) Terminal Seals. Where Type MI cable terminates, an 
end seal fitting shall be installed immediately after stripping 
to prevent the entrance of moisture into the insulation. The 
conductors extending beyond the sheath shall be individu- 
ally provided with an insulating material. 

332.80 Ampacity. The ampacity of Type MI cable shall be 
determined in accordance with 310.15. The conductor tem- 
perature at the end seal fitting shall not exceed the tempera- 
ture rating of the listed end seal fitting, and the installation 
shall not exceed the temperature ratings of terminations or 
equipment. 

(A) Type MI Cable Installed in Cable Tray. The ampaci- 
ties for Type MI cable installed in cable tray shall be deter- 
mined in accordance with 392.11. 

(B) Single Type MI Conductors Grouped Together. 

Where single Type MI conductors are grouped together in a 
triangular or square configuration, as required by 332.31, 
and installed on a messenger or as open runs with a main- 
tained free air space of not less than 2.15 times one con- 
ductor diameter (2.15 x O.D.) of the largest conductor con- 
tained within the configuration and adjacent conductor 
configurations or cables, the ampacity of the conductors 
shall not exceed the allowable ampacities of Table 310.17. 

III. Construction Specifications 

332.104 Conductors. Type MI cable conductors shall be 
of solid copper, nickel, or nickel-coated copper with a re- 
sistance corresponding to standard AWG and kcmil sizes. 

332.108 Equipment Grounding. Where the outer sheath 
is made of copper, it shall provide an adequate path for 



ARTICLE 334 
Nonmetallic-Sheathed Cable: 
Types NM, NMC, and NMS 



I. General 

334.1 Scope. This article covers the use, installation, and 
construction specifications of nonmetallic-sheathed cable. 

334.2 Definition. 

Nonmetallic-Sheathed Cable. A factory assembly of two 
or more insulated conductors having an outer sheath of 
nonmetallic material. 

334.6 Listed. Type NM, Type NMC, and Type NMS 
cables shall be listed. 



II. Installation 

334.10 Uses Permitted. Type NM, Type NMC, and Type 
NMS cables shall be permitted to be used in the following: 

(1) One- and two-family dwellings. 

(2) Multifamily dwellings permitted to be of Types III, IV, 
and V construction except as prohibited in 334.12. 

(3) Other structures permitted to be of Types III, IV, and V 
construction except as prohibited in 334.12. Cables 
shall be concealed within walls, floors, or ceilings that 
provide a thermal barrier of material that has at least a 
15-minute finish rating as identified in listings of fire- 
rated assemblies. 

FPN No. 1: Building constructions are defined in NFPA 
220-1999, Standard on Types of Building Construction, or 
the applicable building code, or both. 

FPN No. 2: See Annex E for determination of building 
types [NFPA 220, Table 3-1]. 

(4) Cable trays, where the cables are identified for the use. 
FPN: See 310.10 for temperature limitation of conductors. 



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ARTICLE 334 — NONMETALLIC-SHEATHED CABLE: TYPES NM, NMC, AND NMS 



70-183 



(A) Type NM. Type NM cable shall be permitted as follows: 

(1) For both exposed and concealed work in normally dry 
locations except as prohibited in 334.10(3). 

(2) To be installed or fished in air voids in masonry block 
or tile walls 

(B) Type NMC. Type NMC cable shall be permitted as 
follows: 

(1) For both exposed and concealed work in dry, moist, 
damp, or corrosive locations, except as prohibited in 
334.10(3) 

(2) In outside and inside walls of masonry block or tile 

(3) In a shallow chase in masonry, concrete, or adobe pro- 
tected against nails or screws by a steel plate at least 
1.59 mm (V\6 in.) thick and covered with plaster, 
adobe, or similar finish 

(C) Type NMS. Type NMS cable shall be permitted as 
follows: 

(1) For both exposed and concealed work in normally dry 
locations except as prohibited in 334.10(3) 

(2) To be installed or fished in air voids in masonry block 
or tile walls 

(3) To be used as permitted in Article 780 

334.12 Uses Not Permitted. 

(A) Types NM, NMC, and NMS. Types NM, NMC, and 
NMS cables shall not be used as follows: 

(1) As open runs in dropped or suspended ceilings in 
other than one- and two-family and multifamily 
dwellings. 

(2) As service-entrance cable. 

(3) In commercial garages having hazardous (classified) 
locations as defined in 511.3. 

(4) In theaters and similar locations, except where permit- 
ted in 518.4. 

(5) In motion picture studios. 

(6) In storage battery rooms. 

(7) In hoistways or on elevators or escalators. 

(8) Embedded in poured cement, concrete, or aggregate. 

(9) In hazardous (classified) locations, except where per- 
mitted in the following: 

a. 501.4(B), Exception 

b. 502.4(B), Exception No. 1 

c. 504.20 

(10) Types NM and NMS. Types NM and NMS cable shall 
not be used as follows: 

a. Where exposed to corrosive fumes or vapors 

b. Where embedded in masonry, concrete, adobe, fill, 
or plaster 

c. In a shallow chase in masonry, concrete, or adobe 
and covered with plaster, adobe, or similar finish 



d. Where exposed or subject to excessive moisture or 
dampness 

334.15 Exposed Work. In exposed work, except as pro- 
vided in 300.11(A), the cable shall be installed as specified 
in 334.15(A) through (C). 

(A) To Follow Surface. The cable shall closely follow the 
surface of the building finish or of running boards. 

(B) Protection from Physical Damage. The cable shall be 
protected from physical damage where necessary by con- 
duit, electrical metallic tubing, Schedule 80 PVC rigid non- 
metallic conduit, pipe, guard strips, listed surface metal or 
nonmetallic raceway, or other means. Where passing 
through a floor, the cable shall be enclosed in rigid metal 
conduit, intermediate metal conduit, electrical metallic tub- 
ing, Schedule 80 PVC rigid nonmetallic conduit, listed sur- 
face metal or nonmetallic raceway, or other metal pipe ex- 
tending at least 150 mm (6 in.) above the floor. 

(C) In Unfinished Basements. Where the cable is run at 
angles with joists in unfinished basements, it shall be per- 
missible to secure cables not smaller than two 6 AWG or 
three 8 AWG conductors directly to the lower edges of the 
joists. Smaller cables shall be run either through bored 
holes in joists or on running boards. 

334.17 Through or Parallel to Framing Members. Types 
NM, NMC, or NMS cable shall be protected in accordance 
with 300.4 where installed through or parallel to framing 
members. Grommets used as required in 300.4(B)(1) shall 
remain in place and be listed for the purpose of cable 
protection. 

334.23 In Accessible Attics. The installation of cable in 
accessible attics or roof spaces shall also comply with 
320.23. 

334.24 Bending Radius. Bends in Types NM, NMC, and 
NMS cable shall be made so that the cable will not be 
damaged. The radius of the curve of the inner edge of any 
bend during or after installation shall not be less than five 
times the diameter of the cable. 

334.30 Securing and Supporting. Nonmetallic-sheathed 
cable shall be secured by staples, cable ties, straps, hangers, 
or similar fittings designed and installed so as not to dam- 
age the cable at intervals not exceeding 1.4 m (4'/2 ft) and 
within 300 mm (12 in.) of every cabinet, box, or fitting. 
Flat cables shall not be stapled on edge. 

(A) Horizontal Runs through Holes and Notches. In 

other than vertical runs, cables installed in accordance with 
300.4 shall be considered supported and secured where 



NATIONAL ELECTRICAL CODE 



2002 Edition 



70-184 



ARTICLE 336 — POWER AND CONTROL TRAY CABLE: TYPE TC 



such support does not exceed 1.4-m (4V2-ft) intervals and 
the nonmetallic-sheathed cable is securely fastened in place 
by an approved means within 300 mm (12 in.) of each box, 
cabinet, conduit body, or other nonmetallic-sheathed cable 
termination. 

FPN: See 314.17(C) for support where nonmetallic boxes 
are used. 

(B) Unsupported Cables. Nonmetallic-sheathed cable 
shall be permitted to be unsupported where the cable: 

(1) Is fished between access points, where concealed in 
finished buildings or finished panels for prefabricated 
buildings and supporting is impracticable 

(2) Is not more than 1.4 m (4V2 ft) from the last point of 
support for connections within an accessible ceiling to 
luminaire(s) [lighting fixture(s)] or equipment 

(C) Wiring Device Without a Separate Outlet Box. A 

wiring device identified for the use, without a separate out- 
let box, incorporating an integral cable clamp shall be per- 
mitted where the cable is secured in place at intervals not 
exceeding 1.4 m (4V2 ft) and within 300 mm (12 in.) from 
the wiring device wall opening, and there shall be at least a 
300 mm (12 in.) loop of unbroken cable or 150 mm (6 in.) 
of a cable end available on the interior side of the finished 
wall to permit replacement. 



334.40 Boxes and Fittings. 

(A) Boxes of Insulating Material. Nonmetallic 
boxes shall be permitted as provided in 314.3. 



outlet 



(B) Devices of Insulating Material. Switch, outlet, and 
tap devices of insulating material shall be permitted to be 
used without boxes in exposed cable wiring and for rewir- 
ing in existing buildings where the cable is concealed and 
fished. Openings in such devices shall form a close fit 
around the outer covering of the cable, and the device shall 
fully enclose the part of the cable from which any part of 
the covering has been removed. Where connections to con- 
ductors are by binding-screw terminals, there shall be avail- 
able as many terminals as conductors. 

(C) Devices with Integral Enclosures. Wiring devices 
with integral enclosures identified for such use shall be 
permitted as provided in 300.15(E). 

334.80 Ampacity. The ampacity of Types NM, NMC, and 
NMS cable shall be determined in accordance with 310.15. 
The ampacity shall be in accordance with the 60°C (140°F) 
conductor temperature rating. The 90°C (194°F) rating 
shall be permitted to be used for ampacity derating pur- 
poses, provided the final derated ampacity does not exceed 
that for a 60°C (140°F) rated conductor. The ampacity of 



Types NM, NMC, and NMS cable installed in cable tray 
shall be determined in accordance with 392.11. 



III. Construction Specifications 

334.100 Construction. The outer cable sheath of 
nonmetallic-sheathed cable shall be a nonmetallic material. 

334.104 Conductors. The insulated power conductors 
shall be sizes 14 AWG through 2 AWG with copper con- 
ductors or sizes 12 AWG through 2 AWG with aluminum or 
copper-clad aluminum conductors. The signaling conduc- 
tors shall comply with 780.5. 

334.108 Equipment Grounding. In addition to the insu- 
lated conductors, the cable shall be permitted to have an 
insulated or bare conductor for equipment grounding pur- 
poses only. Where provided, the grounding conductor shall 
be sized in accordance with Article 250. 

334.112 Insulation. The insulated power conductors shall be 
one of the types listed in Table 310.13 that is suitable for 
branch circuit wiring or one that is identified for use in 
these cables. Conductor insulation shall be rated at 90°C 
(194°F). 

FPN: Types NM, NMC, and NMS cable identified by the 
markings NM-B, NMC-B, and NMS-B meet this 
requirement. 

334.116 Sheath. The outer sheath of nonmetallic-sheathed 
cable shall comply with 334.116(A), (B), and (C). 

(A) Type NM. The overall covering shall be flame retar- 
dant and moisture resistant. 

(B) Type NMC. The overall covering shall be flame retar- 
dant, moisture resistant, fungus resistant, and corrosion re- 
sistant. 

(C) Type NMS. The overall covering shall be flame retar- 
dant and moisture resistant. The sheath shall be applied so 
as to separate the power conductors from the communica- 
tions and signaling conductors. The signaling conductors 
shall be permitted to be shielded. An optional outer jacket 
shall be permitted. 

FPN: For composite optical cable, see 770.5 and 770.52. 



ARTICLE 336 
Power and Control Tray Cable: Type TC 

I. General 

336.1 Scope. This article covers the use, installation, and 
construction specifications for power and control tray cable, 
Type TC. 



• 



2002 Edition 



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ARTICLE 336 — POWER AND CONTROL TRAY CABLE: TYPE TC 



70-185 



336.2 Definition. 

Power and Control Tray Cable, Type TC. A factory as- 
sembly of two or more insulated conductors, with or with- 
out associated bare or covered grounding conductors, under 
a nonmetallic jacket, for installation in cable trays, in race- 
ways, or where supported by a messenger wire. 

II. Installation 

336.10 Uses Permitted. Type TC tray cable shall be per- 
mitted to be used in the following: 

(1) For power, lighting, control, and signal circuits. 

(2) In cable trays, or in raceways, or where supported in 
outdoor locations by a messenger wire. 

(3) In cable trays in hazardous (classified) locations as per- 
mitted in Articles 392, 501, 502, 504, and 505 in indus- 
trial establishments where the conditions of mainte- 
nance and supervision ensure that only qualified 
persons service the installation. 

(4) For Class I circuits as permitted in Article 725. 

(5) For non-power-limited fire alarm circuits if conductors 
comply with the requirements of 760.27. 

(6) In industrial establishments where the conditions of main- 
tenance and supervision ensure that only qualified persons 
service the installation, and where the cable is continu- 
ously supported and protected against physical damage 
using mechanical protection, such as struts, angles, or 
channel, Type TC tray cable that complies with the crush 
and impact requirements of Type MC cable and is identi- 
fied for such use shall be permitted between a cable tray 
and the utilization equipment or device. The cable shall be 
secured at intervals not exceeding 1.8 m (6 ft). Equipment 
grounding for the utilization equipment shall be provided 
by an equipment grounding conductor within the cable, hi 
cables containing conductors size 6 AWG or smaller, the 
equipment grounding conductor shall be provided within 
the cable or, at the time of installation, one or more insu- 
lated conductors shall be permanently identified as an 
equipment grounding conductor in accordance with 
250.119(B). 

(7) Where installed in wet locations, Type TC cable shall 
also be resistant to moisture and corrosive agents. 

FPN: See 310.10 for temperature limitation of conductors. 

336.12 Uses Not Permitted. Type TC tray cable shall not 
be used in the following: 

(1) Installed where it will be exposed to physical damage 

(2) Installed as open cable on brackets or cleats, except as 
permitted in 340.10(6) 

(3) Used where exposed to direct rays of the sun, unless 
identified as sunlight resistant 

(4) Direct buried, unless identified for such use 



336.24 Bending Radius. Bends in Type TC cable shall be 
made so as not to damage the cable. For Type TC cable 
without metal shielding, the minimum bending radius shall 
be as follows: 

(1) Four times the overall diameter for cables 25 mm 
(1 in.) or less in diameter 

(2) Five times the overall diameter for cables larger than 
25 mm (1 in.) but not more than 50 mm (2 in.) in 
diameter 

(3) Six times the overall diameter for cables larger than 50 
mm (2 in.) in diameter 

Type TC cables with metallic shielding shall have a 
minimum bending radius of not less than 12 times the cable 
overall diameter. 

336.80 Ampacity. The ampacity of Type TC tray cable 
shall be determined in accordance with 392.11 for 14 AWG 
and larger conductors, in accordance with 402.5 for 18 
AWG through 16 AWG conductors where installed in cable 
tray, and in accordance with 310.15 where installed in a 
raceway or as messenger supported wiring. 

III. Construction Specifications 

336.100 Construction. A metallic sheath or armor as de- 
fined in 330.116 shall not be permitted either under or over 
the nonmetallic jacket. Metallic shield(s) shall be permitted 
over groups of conductors, under the outer jacket, or both. 

336.104 Conductors. The insulated conductors of Type 
TC tray cable shall be in sizes 18 AWG through 1000 kcmil 
copper and sizes 12 AWG through 1000 kcmil aluminum or 
copper-clad aluminum. Insulated conductors of sizes 14 
AWG and larger copper and sizes 12 AWG and larger alu- 
minum or copper-clad aluminum shall be one of the types 
listed in Table 310.13 or Table 310.62 that is suitable for 
branch circuit and feeder circuits or one that is identified 
for such use. 

(A) Fire Alarm Systems. Where used for fire alarm sys- 
tems, conductors shall also be in accordance with 760.27. 

(B) Thermocouple Circuits. Conductors in Type TC 
cables used for thermocouple circuits in accordance with 
Article 725 shall also be permitted to be any of the mate- 
rials used for thermocouple extension wire. 

(C) Class I Circuit Conductors. Insulated conductors of 
18 AWG and 16 AWG copper shall also be in accordance 
with 725.27. 

336.116 Jacket. The outer jacket shall be a flame- 
retardant, nonmetallic material. 

336.120 Marking. There shall be no voltage marking on a 
Type TC cable employing thermocouple extension wire. 



NATIONAL ELECTRICAL CODE 



2002 Edition 



70-186 



ARTICLE 338 — SERVICE-ENTRANCE CABLE: TYPES SE AND USE 



ARTICLE 338 

Service-Entrance Cable: 

Types SE and USE 



I. General 



338.1 Scope. This article covers the use, installation, and 
construction specifications of service-entrance cable. 

338.2 Definitions. 

Service-Entrance Cable. A single conductor or multicon- 
ductor assembly provided with or without an overall cov- 
ering, primarily used for services, and of the following 
types: 

Type SE. Service-entrance cable having a flame-retardant, 
moisture-resistant covering. 

Type USE. Service-entrance cable, identified for under- 
ground use, having a moisture-resistant covering, but not 
required to have a flame-retardant covering. 

II. Installation 
338.10 Uses Permitted. 

(A) Service-Entrance Conductors. Service-entrance cable 
used as service-entrance conductors shall be installed as 
required by Article 230. 

Type USE used for service laterals shall be permitted to 
emerge from the ground outside at terminations in meter 
bases or other enclosures where protected in accordance 
with 300.5(D). 

(B) Branch Circuits or Feeders. 

(1) Grounded Conductor Insulated. Type SE service- 
entrance cables shall be permitted in wiring systems where 
all of the circuit conductors of the cable are of the rubber- 
covered or thermoplastic type. 

(2) Grounded Conductor Not Insulated. Type SE 
service-entrance cable shall be permitted for use where the 
insulated conductors are used for circuit wiring and the 
uninsulated conductor is used only for equipment ground- 
ing purposes. 

Exception: Uninsulated conductors shall be permitted as a 
grounded conductor in accordance with 250.140. 

(3) Temperature Limitations. Type SE service-entrance 
cable used to supply appliances shall not be subject to con- 
ductor temperatures in excess of the temperature specified 
for the type of insulation involved. 



(4) Installation Methods for Branch Circuits and 
Feeders. 

(a) Interior Installations. In addition to the provisions 
of this article, Type SE service-entrance cable used for in- 
terior wiring shall comply with the installation require- 
ments of Parts I and II of Article 334, excluding 334.80. 

FPN: See 310.10 for temperature limitation of conductors. 

(b) Exterior Installations. In addition to the provisions 
of this article, service-entrance cable used for feeders or 
branch circuits, where installed as exterior wiring, shall be 
installed as required by Article 225. The cable shall be 
supported in accordance with 334.30, unless used as 
messenger-supported wiring as allowed by Article 396. 

Type USE cable shall be installed outside in accordance 
with the provisions of Article 340. Where Type USE cable 
emerges from the ground at terminations, it shall be pro- 
tected in accordance with 300.5(D). 

Multiconductor service-entrance cable shall be permit- 
ted to be installed as messenger-supported wiring in accor- 
dance with Articles 225 and 396. 

338.24 Bending Radius. Bends in Types USE and SE 
cable shall be made so that the cable will not be damaged. 
The radius of the curve of the inner edge of any bend, 
during or after installation, shall not be less than five times 
the diameter of the cable. 



III. Construction 

338.100 Construction. Cabled, single-conductor, Type USE 
constructions recognized for underground use shall be permit- 
ted to have a bare copper conductor cabled with the assembly. 
Type USE single, parallel, or cabled conductor assemblies rec- 
ognized for underground use shall be permitted to have a bare 
copper concentric conductor applied. These constructions shall 
not require an outer overall covering. 

FPN: See 230.41, Exception, item (b), for directly buried, 
uninsulated service-entrance conductors. 

Type SE or USE cable containing two or more conduc- 
tors shall be permitted to have one conductor uninsulated. 

338.120 Marking. Service-entrance cable shall be marked 
as required in 310.11. Cable with the neutral conductor 
smaller than the ungrounded conductors shall be so 
marked. 



2002 Edition 



NATIONAL ELECTRICAL CODE 



ARTICLE 342 — INTERMEDIATE METAL CONDUIT: TYPE IMC 



70-187 



ARTICLE 340 
Cable: Type UF 

I. General 

340.1 Scope. This article covers the use, installation, and 
construction specifications for underground feeder and 
branch-circuit cable, Type UF. 

340.2 Definition. 

Underground Feeder and Branch-Circuit Cable, Type 

UF. A listed factory assembly of one or more insulated 
conductors with an integral or an overall covering of non- 
metallic material suitable for direct burial in the earth. 



(8) Embedded in poured cement, concrete, or aggregate, 
except where embedded in plaster as nonheating leads 
where permitted in 424.43 

(9) Where exposed to direct rays of the sun, unless iden- 
tified as sunlight resistant 

(10) Where subject to physical damage 

(11) As overhead cable, except where installed as 
messenger-supported wiring in accordance with Ar- 
ticle 396 

340.24 Bending Radius. Bends in Type UF cable shall be 
made so that the cable shall not be damaged. The radius of 
the curve of the inner edge of any bend shall not be less 
than five times the diameter of the cable. 

340.80 Ampacity. The ampacity of Type UF cable shall be 
that of 60°C (140°F) conductors in accordance with 310.15. 



II. Installation 

340.10 Uses Permitted. Type UF cable shall be permitted 
as follows: 

(1) For use underground, including direct burial in the 
earth. For underground requirements, see 300.5 

(2) As single-conductor cables. Where installed as single- 
conductor cables, all conductors of the feeder grounded 
conductor or branch circuit, including the grounded 
conductor and equipment grounding conductor, if any, 
shall be installed in accordance with 300.3. 

(3) For wiring in wet, dry, or corrosive locations under the 
recognized wiring methods of this Code. 

(4) Installed as nonmetallic-sheathed cable. Where so in- 
stalled, the installation and conductor requirements 
shall comply with the provisions of Article 334 and 
shall be of the multiconductor type. 

(5) For solar photovoltaic systems in accordance with 
690.31. 

(6) As single-conductor cables as the nonheating leads for 
heating cables as provided in 424.43. 

(7) Supported by cable trays. Type UF cable supported by 
cable trays shall be of the multiconductor type. 

FPN: See 310.10 for temperature limitation of conductors. 

340.12 Uses Not Permitted. Type UF cable shall not be 
used as follows: 

(1) As service-entrance cable 

(2) In commercial garages 

(3) In theaters and similar locations 

(4) In motion picture studios 

(5) In storage battery rooms 

(6) In hoistways, or on elevators or escalators 

(7) In hazardous (classified) locations 



III. Construction Specifications 

340.104 Conductors. The conductors shall be sizes 14 
AWG copper or 12 AWG aluminum or copper-clad alumi- 
num through 4/0 AWG. 

340.108 Fquipment Grounding. In addition to the insu- 
lated conductors, the cable shall be permitted to have an 
insulated or bare conductor for equipment grounding pur- 
poses only. 

340.112 Insulation. The conductors of Type UF shall be 
one of the moisture-resistant types listed in Table 310.13 
that is suitable for branch-circuit wiring or one that is iden- 
tified for such use. 

340.116 Sheath. The overall covering shall be flame retar- 
dant; moisture, fungus, and corrosion resistant; and suitable 
for direct burial in the earth. 






I. General 

342.1 Scope. This article covers the use, installation, and 
construction specifications for intermediate metal conduit 
(IMC) and associated fittings. 

342.2 Definition. 

Intermediate Metal Conduit (IMC). A steel threadable 
raceway of circular cross section designed for the physical 
protection and routing of conductors and cables and for use 



NATIONAL ELECTRICAL CODE 



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70-188 



ARTICLE 342 — INTERMEDIATE METAL CONDUIT: TYPE IMC 



as an equipment grounding conductor when installed with 
its integral or associated coupling and appropriate fittings. 

342.6 Listing Requirements. IMC, factory elbows and 
couplings, and associated fittings shall be listed. 

II. Installation 
342.10 Uses Permitted. 

(A) All Atmospheric Conditions and Occupancies. Use 

of IMC shall be permitted under all atmospheric conditions 
and occupancies. 

(B) Corrosion Environments. IMC, elbows, couplings, 
and fittings shall be permitted to be installed in concrete, in 
direct contact with the earth, or in areas subject to severe 
corrosive influences where protected by corrosion protec- 
tion and judged suitable for the condition. 

(C) Cinder Fill. IMC shall be permitted to be installed in 
or under cinder fill where subject to permanent moisture 
where protected on all sides by a layer of noncinder con- 
crete not less than 50 mm (2 in.) thick; where the conduit is 
not less than 450 mm (18 in.) under the fill; or where 
protected by corrosion protection and judged suitable for 
the condition. 

(D) Wet Locations. All supports, bolts, straps, screws, and 
so forth, shall be of corrosion-resistant materials or pro- 
tected against corrosion by corrosion-resistant materials. 

FPN: See 300.6 for protection against corrosion. 

342.14 Dissimilar Metals. Where practicable, dissimilar 
metals in contact anywhere in the system shall be avoided 
to eliminate the possibility of galvanic action. 

Aluminum fittings and enclosures shall be permitted to 
be used with IMC. 

342.20 Size. 

(A) Minimum. IMC smaller than metric designator 16 
(trade size Vi) shall not be used. 

(B) Maximum. IMC larger than metric designator 103 
(trade size 4) shall not be used. 

FPN: See 300.1(C) for the metric designators and trade 
sizes. These are for identification purposes only and do not 
relate to actual dimensions. 

342.22 Number of Conductors. The number of conduc- 
tors shall not exceed that permitted by the percentage fill 
specified in Table 1, Chapter 9. 

Cables shall be permitted to be installed where such use 
is permitted by the respective cable articles. The number of 



cables shall not exceed the allowable percentage fill speci- 
fied in Table 1, Chapter 9. 

342.24 Bends — How Made. Bends of IMC shall be 
made so that the conduit will not be damaged and so that 
the internal diameter of the conduit will not be effectively 
reduced. The radius of the curve of any field bend to the 
centerline of the conduit shall not be less than indicated in 
Table 344.24. 

342.26 Bends — Number in One Run. There shall not be 
more than the equivalent of four quarter bends (360 degrees 
total) between pull points, for example, conduit bodies and 
boxes. 

342.28 Reaming and Threading. All cut ends shall be 
reamed or otherwise finished to remove rough edges. 
Where conduit is threaded in the field, a standard cutting 
die with a taper of 1 in 16 ( 3 A in. taper per foot) shall be 
used. 

FPN: See ANSI/ASME B. 1.20. 1-1983, Standard for Pipe 
Threads, General Purpose (Inch). 

342.30 Securing and Supporting. IMC shall be installed 
as a complete system as provided in Article 300 and shall 
be securely fastened in place and supported in accordance 
with 342.30(A) and (B). 

(A) Securely Fastened. Each IMC shall be securely fas- 
tened within 900 mm (3 ft) of each outlet box, junction 
box, device box, cabinet, conduit body, or other conduit 
termination. Fastening shall be permitted to be increased to 
a distance of 1.5 m (5 ft) where structural members do not 
readily permit fastening within 900 mm (3 ft). Where ap- 
proved, conduit shall not be required to be securely fas- 
tened within 900 mm (3 ft) of the service head for above- 
the-roof termination of a mast. 

(B) Supports. IMC shall be supported in accordance with 
one of the following: 

(1) Conduit shall be supported at intervals not exceeding 3 
m (10 ft). 

(2) The distance between supports for straight runs of con- 
duit shall be permitted in accordance with Table 
344.30(B)(2), provided the conduit is made up with 
threaded couplings and such supports prevent transmis- 
sion of stresses to termination where conduit is de- 
flected between supports. 

(3) Exposed vertical risers from industrial machinery or fixed 
equipment shall be permitted to be supported at intervals 
not exceeding 6 m (20 ft), if the conduit is made up with 
threaded couplings, the conduit is firmly supported at the 
top and bottom of the riser, and no other means of inter- 
mediate support is readily available. 



2002 Edition 



NATIONAL ELECTRICAL CODE 



ARTICLE 344 — RIGID METAL CONDUIT: TYPE RMC 



70-189 



(4) Horizontal runs of IMC supported by openings through 
framing members at intervals not exceeding 3 m (10 ft) 
and securely fastened within 900 mm (3 ft) of termina- 
tion points shall be permitted. 

342.42 Couplings and Connectors. 

(A) Threadless. Threadless couplings and connectors used 
with conduit shall be made tight. Where buried in masonry 
or concrete, they shall be the concretetight type. Where 
installed in wet locations, they shall be the raintight type. 
Threadless couplings and connectors shall not be used on 
threaded conduit ends unless listed for the purpose. 

(B) Running Threads. Running threads shall not be used 
on conduit for connection at couplings. 

342.46 Bushings. Where a conduit enters a box, fitting, or 
other enclosure, a bushing shall be provided to protect the 
wire from abrasion unless the design of the box, fitting, or 
enclosure is such as to afford equivalent protection. 

FPN: See 300.4(F) for the protection of conductors 4 AWG 
and larger at bushings. 

342.56 Splices and Taps. Splices and taps shall be made 
in accordance with 300.15. 

342.60 Grounding. IMC shall be permitted as an equip- 
ment grounding conductor. 

III. Construction Specifications 

342.120 Marking. Each length shall be clearly and dura- 
bly marked at least every 1.5 m (5 ft) with the letters IMC. 
Each length shall be marked as required in 110.21. 

342.130 Standard Lengths. The standard length of IMC 
shall be 3.05 m (10 ft), including an attached coupling, and 
each end shall be threaded. Longer or shorter lengths with 
or without coupling and threaded or unthreaded shall be 
permitted. 



ARTICLE 344 

I. General 

344.1 Scope. This article covers the use, installation, and 
construction specifications for rigid metal conduit (RMC) 
and associated fittings. 



344.2 Definition. 

Rigid Metal Conduit (RMC). A threadable raceway of 
circular cross section designed for the physical protection 
and routing of conductors and cables and for use as an 
equipment grounding conductor when installed with its in- 
tegral or associated coupling and appropriate fittings. RMC 
is generally made of steel (ferrous) with protective coatings 
or aluminum (nonferrous). Special use types are silicon 
bronze and stainless steel. 

344.6 Listing Requirements. RMC, factory elbows and 
couplings, and associated fittings shall be listed. 

II. Installation 
344.10 Uses Permitted. 

(A) All Atmospheric Conditions and Occupancies. Use 

of RMC shall be permitted under all atmospheric condi- 
tions and occupancies. Ferrous raceways and fittings pro- 
tected from corrosion solely by enamel shall be permitted 
only indoors and in occupancies not subject to severe cor- 
rosive influences. 

(B) Corrosion Environments. RMC, elbows, couplings, 
and fittings shall be permitted to be installed in concrete, in 
direct contact with the earth, or in areas subject to severe 
corrosive influences where protected by corrosion protec- 
tion and judged suitable for the condition. 

(C) Cinder Fill. RMC shall be permitted to be installed in 
or under cinder fill where subject to permanent moisture 
where protected on all sides by a layer of noncinder con- 
crete not less than 50 mm (2 in.) thick; where the conduit is 
not less than 450 mm (18 in.) under the fill; or where 
protected by corrosion protection and judged suitable for 
the condition. 

(D) Wet Locations. All supports, bolts, straps, screws, and 
so forth, shall be of corrosion-resistant materials or pro- 
tected against corrosion by corrosion-resistant materials. 

FPN: See 300.6 for protection against corrosion. 

344.14 Dissimilar Metals. Where practicable, dissimilar 
metals in contact anywhere in the system shall be avoided 
to eliminate the possibility of galvanic action. Aluminum 
fittings and enclosures shall be permitted to be used with 
steel RMC, and steel fittings and enclosures shall be per- 
mitted to be used with aluminum RMC where not subject to 
severe corrosive influences. 

344.20 Size. 

(A) Minimum. RMC smaller than metric designator 16 
(trade size Vi) shall not be used. 



NATIONAL ELECTRICAL CODE 



2002 Edition 



70-190 



ARTICLE 344 — RIGID METAL CONDUIT: TYPE RMC 



Exception: For enclosing the leads of motors as permitted 
in 430.145(B). 

(B) Maximum. RMC larger than metric designator 155 
(trade size 6) shall not be used. 

FPN: See 300.1(C) for the metric designators and trade 
sizes. These are for identification purposes only and do not 
relate to actual dimensions. 

344.22 Number of Conductors. The number of conduc- 
tors or cables shall not exceed that permitted by the per- 
centage fill specified in Table 1, Chapter 9. 

Cables shall be permitted to be installed where such use 
is permitted by the respective cable articles. The number of 
cables shall not exceed the allowable percentage fill speci- 
fied in Table 1, Chapter 9. 

344.24 Bends — How Made. Bends of RMC shall be 
made so that the conduit is not damaged and the internal 
diameter of the conduit is not effectively reduced. The ra- 
dius of the curve of any field bend to the centerline of the 
conduit shall not be less than indicated in Table 344.24. 

Table 344.24 Radius of Conduit Bends 



Conduit Size 

Metric Trade 

Designator Size 



One Shot and 

Full Shoe 

Benders 



in. 



Other Bends 



16 

21 

27 

35 

41 

53 

63 

78 

91 

103 

129 

155 



>/2 
3/4 
1 

VA 

V/2 

2 

2Vi 

3 

3V2 

4 

5 

6 



101.6 

114.3 

146.05 

184.15 

209.55 

241.3 

266.7 

330.2 

381 

406.4 

609.6 

762 



4 

4 l A 

5 3 A 
IVa 

8'/4 

9Vl 

\QVi 

13 

15 

16 

24 

30 



101.6 

127 

152.4 

203.2 

254 

304.8 

381 

457.2 

533.4 

609.6 

762 

914.4 



4 
5 
6 
8 

10 
12 
15 
18 
21 
24 
30 
36 



344.26 Bends — Number in One Run. There shall not be 
more than the equivalent of four quarter bends (360 degrees 
total) between pull points, for example, conduit bodies and 
boxes. 

344.28 Reaming and Threading. All cut ends shall be 
reamed or otherwise finished to remove rough edges. 
Where conduit is threaded in the field, a standard cutting 
die with a 1 in 16 taper ( 3 /4-in. taper per foot) shall be used. 

FPN: See ANSI/ASME B. 1.20. 1-1983, Standard for Pipe 
Threads, General Purpose (Inch). 



344.30 Securing and Supporting. RMC shall be installed 
as a complete system as provided in Article 300 and shall 
be securely fastened in place and supported in accordance 
with 344.30(A) and (B). 

(A) Securely Fastened. RMC shall be securely fastened 
within 900 mm (3 ft) of each outlet box, junction box, 
device box, cabinet, conduit body, or other conduit termi- 
nation. Fastening shall be permitted to be increased to a 
distance of 1.5 m (5 ft) where structural members do not 
readily permit fastening within 900 mm (3 ft). Where ap- 
proved, conduit shall not be required to be securely fas- 
tened within 900 mm (3 ft) of the service head for above- 
the-roof termination of a mast. 

(B) Supports. RMC shall be supported in accordance with 
one of the following. 

(1) Conduit shall be supported at intervals not exceeding 
3 m (10 ft). 

(2) The distance between supports for straight runs of con- 
duit shall be permitted in accordance with Table 
344.30(B)(2), provided the conduit is made up with 
threaded couplings, and such supports prevent trans- 
mission of stresses to termination where conduit is de- 
flected between supports. 

(3) Exposed vertical risers from industrial machinery or 
fixed equipment shall be permitted to be supported at 
intervals not exceeding 6 m (20 ft), if the conduit is 
made up with threaded couplings, the conduit is firmly 
supported at the top and bottom of the riser, and no 
other means of intermediate support is readily avail- 
able. 

(4) Horizontal runs of RMC supported by openings through 
framing members at intervals not exceeding 3 m (10 ft) 
and securely fastened within 900 mm (3 ft) of termination 
points shall be permitted. 

Table 344.30(B)(2) Supports for Rigid Metal Conduit 



Conduit Size 



Maximum Distance 

Between Rigid Metal 

Conduit Supports 



Metric 
Designator 



Trade Size 



m 



ft 



16-21 
27 
35-41 
53-63 



'/2- 3 /4 

1 

VA-V/l 

2-2V2 



78 and larger 3 and larger 



3.0 
3.7 
4.3 
4.9 
6.1 



10 
12 
14 
16 
20 



344.42 Couplings and Connectors. 

(A) Threadless. Threadless couplings and connectors used 
with conduit shall be made tight. Where buried in masonry 



2002 Edition 



NATIONAL ELECTRICAL CODE 



ARTICLE 348 — FLEXIBLE METAL CONDUIT: TYPE FMC 



70-191 



or concrete, they shall be the concretetight type. Where 
installed in wet locations, they shall be the raintight type, 
Threadless couplings and connectors shall not be used on 
threaded conduit ends unless listed for the purpose. 

(B) Running Threads. Running threads shall not be used 
on conduit for connection at couplings. 

344.46 Bushings. Where a conduit enters a box, fitting, or 
other enclosure, a bushing shall be provided to protect the 
wire from abrasion unless the design of the box, fitting, or 
enclosure is such as to afford equivalent protection. 

FPN: See 300.4(F) for the protection of conductors sizes 4 
AWG and larger at bushings. 

344.56 Splices and Taps. Splices and taps shall be made 
in accordance with 300.15. 

344.60 Grounding. RMC shall be permitted as an equip- 
ment grounding conductor. 

III. Construction Specifications 

344.120 Marking. Each length shall be clearly and dura- 
bly identified in every 3 m (10 ft) as required in the first 
sentence of 110.21. Nonferrous conduit of corrosion- 
resistant material shall have suitable markings. 

344.130 Standard Lengths. The standard length of RMC 
shall be 3.05 m (10 ft), including an attached coupling, and 
each end shall be threaded. Longer or shorter lengths with 
or without coupling and threaded or unthreaded shall be 
permitted. 



ARTICLE 348 
Flexible Metal Conduit: Type FMC 



I. General 

348.1 Scope. This article covers the use, installation, and 
construction specifications for flexible metal conduit 
(FMC) and associated fittings. 

348.2 Definition. 

Flexible Metal Conduit (FMC). A raceway of circular 
cross section made of helically wound, formed, interlocked 
metal strip. 

348.6 Listing Requirements. FMC and associated fittings 
shall be listed. 



II. Installation 

348.10 Uses Permitted. FMC shall be permitted to be 
used in exposed and concealed locations. 

348.12 Uses Not Permitted. FMC shall not be used in the 
following: 

(1) In wet locations unless the conductors are approved for 
the specific conditions and the installation is such that 
liquid is not likely to enter raceways or enclosures to 
which the conduit is connected 

(2) In hoistways, other than as permitted in 620.21(A)(1) 

(3) In storage battery rooms 

(4) In any hazardous (classified) location other than as per- 
mitted in 501.4(B) and 504.20 

(5) Where exposed to materials having a deteriorating ef- 
fect on the installed conductors, such as oil or gasoline 

(6) Underground or embedded in poured concrete or aggre- 
gate 

(7) Where subject to physical damage 

348.20 Size. 

(A) Minimum. FMC less than metric designator 16 (trade 
size Vt) shall not be used unless permitted in 348.20(A)(1) 
through (5) for metric designator 12 (trade size V&). 

(1) For enclosing the leads of motors as permitted in 
430.145(B) 

(2) In lengths not in excess of 1.8 m (6 ft) for any of the 
following uses: 

a. For utilization equipment 

b. As part of a listed assembly 

c. For tap connections to luminaires (lighting fixtures) 
as permitted in 410.67(C) 

(3) For manufactured wiring systems as permitted in 
604.6(A) 

(4) In hoistways as permitted in 620.21(A)(1) 

(5) As part of a listed assembly to connect wired luminaire 
(fixture) sections as permitted in 410.77(C) 

(B) Maximum. FMC larger than metric designator 103 
(trade size 4) shall not be used. 

FPN: See 300.1(C) for the metric designators and trade 
sizes. These are for identification purposes only and do not 
relate to actual dimensions. 

348.22 Number of Conductors. The number of conduc- 
tors shall not exceed that permitted by the percentage fill 
specified in Table 1, Chapter 9, or as permitted in Table 
348.22 for metric designator 12 (trade size 3 /s). 

Cables shall be permitted to be installed where such use 
is permitted by the respective cable articles. The number of 
cables shall not exceed the allowable percentage fill speci- 
fied in Table 1, Chapter 9. 



NATIONAL ELECTRICAL CODE 



2002 Edition 



70-192 



ARTICLE 350 — LIQUIDTIGHT FLEXIBLE METAL CONDUIT: TYPE LFMC 



Table 348.22 Maximum Number of Insulated Conductors in Metric Designator 12 
(Trade Size 3 /s) Flexible Metal Conduit* 





Types RFH-2, SF-2 


Types TF, 

Fittings 
Inside 


XHHW, TW 

Fittings 
Outside 


Types TFN, THHN, 
THWN 


Types FEP, FEBP, PF, 
PGF 


Size 


Fittings 
Inside 


Fittings 
Outside 


Fittings 
Inside 


Fittings 
Outside 


Fittings 
Inside 


Fittings 
Outside 


(AWG) 


Conduit 


Conduit 


Conduit 


Conduit 


Conduit 


Conduit 


Conduit 


Conduit 


18 


2 


3 


3 


5 


5 


8 


5 


8 


16 


1 


2 


3 


4 


4 


6 


4 


6 


14 


1 


2 


2 


3 


3 


4 


3 


4 


12 


— 


— 


1 


2 


2 


3 


2 


3 


10 


— 


— 


1 


1 


1 


1 


1 


2 



*In addition, one covered or bare equipment grounding conductor of the same size shall be permitted. 



348.24 Bends — How Made. Bends in conduit shall be 
made so that the conduit is not damaged and the internal 
diameter of the conduit is not effectively reduced. Bends 
shall be permitted to be made manually without auxiliary 
equipment. The radius of the curve to the centerline of any 
bend shall not be less than shown in Table 344.24 using the 
column "Other Bends." 

348.26 Bends — Number in One Run. There shall not be 
more than the equivalent of four quarter bends (360 degrees 
total) between pull points, for example, conduit bodies and 
boxes. 

348.28 Trimming. All cut ends shall be trimmed or other- 
wise finished to remove rough edges, except where fittings 
that thread into the convolutions are used. 



348.42 Couplings and Connectors. Angle connectors 
shall not be used for concealed raceway installations. 

348.56 Splices and Taps. Splices and taps shall be made 
in accordance with 300.15. 

348.60 Grounding and Bonding. Where used to connect 
equipment where flexibility is required, an equipment 
grounding conductor shall be installed. 

Where required or installed, equipment grounding con- 
ductors shall be installed in accordance with 250.134(B). 

Where required or installed, equipment bonding jump- 
ers shall be installed in accordance with 250.102. 



348.30 Securing and Supporting. FMC shall be securely 
fastened in place and supported in accordance with 
348.30(A) and (B). 

(A) Securely Fastened. FMC shall be securely fastened in 
place by an approved means within 300 mm (12 in.) of 
each box, cabinet, conduit body, or other conduit termina- 
tion and shall be supported and secured at intervals not to 
exceed 1.4 m (4'/2 ft). 

Exception No. 1: Where FMC is fished. 

Exception No. 2: Lengths not exceeding 900 mm (3 ft) at 
terminals where flexibility is required. 

Exception No. 3: Lengths not exceeding 1.8 m (6 ft) from a 
luminaire (fixture) terminal connection for tap connections 
to luminaires (light fixtures) as permitted in 410.67(C). 

(B) Supports. Horizontal runs of flexible metal conduit 
FMC supported by openings through framing members at 
intervals not greater than 1.4 m (4V2 ft) and securely fas- 
tened within 300 mm (12 in.) of termination points shall be 
permitted. 



ARTICLE 350 

Liquidtight Flexible Metal Conduit: 

Type LFMC 

I. General 

350.1 Scope. This article covers the use, installation, and 
construction specifications for liquidtight flexible metal 
conduit (LFMC) and associated fittings. 

350.2 Definition. 

Liquidtight Flexible Metal Conduit (LFMC). A raceway 
of circular cross section having an outer liquidtight, non- 
metallic, sunlight-resistant jacket over an inner flexible 
metal core with associated couplings, connectors, and fit- 
tings for the installation of electric conductors. 

350.6 Listing Requirements. LFMC and associated fit- 
tings shall be listed. 



2002 Edition 



NATIONAL ELECTRICAL CODE 



ARTICLE 350 — LIQUIDTIGHT FLEXIBLE METAL CONDUIT: TYPE LFMC 



70-193 



II. Installation 

350.10 Uses Permitted. LFMC shall be permitted to be 
used in exposed or concealed locations as follows: 

(1) Where conditions of installation, operation, or mainte- 
nance require flexibility or protection from liquids, va- 
pors, or solids 

(2) As permitted by 501.4(B), 502.4, 503.3, and 504.20 
and in other hazardous (classified) locations where spe- 
cifically approved, and by 553.7(B) 

(3) For direct burial where listed and marked for the 
purpose 

350.12 Uses Not Permitted. LFMC shall not be used as 
follows: 

(1) Where subject to physical damage 

(2) Where any combination of ambient and conductor tem- 
perature produces an operating temperature in excess 
of that for which the material is approved 

350.20 Size. 

(A) Minimum. LFMC smaller than metric designator 16 
(trade size Vi) shall not be used. 

Exception: LFMC of metric designator 12 (trade size Vs) 
shall be permitted as covered in 348.20(A). 

(B) Maximum. The maximum size of LFMC shall be met- 
ric designator 103 (trade size 4). 

FPN: See 300.1(C) for the metric designators and trade 
sizes. These are for identification purposes only and do not 
relate to actual dimensions. 



centerline of any bend shall not be less than shown in Table 
344.24 using the column "Other Bends." 

350.26 Bends — Number in One Run. There shall not be 
more than the equivalent of four quarter bends (360 degrees 
total) between pull points, for example, conduit bodies and 
boxes. 

350.30 Securing and Supporting. LFMC shall be se- 
curely fastened in place and supported in accordance with 
350.30(A) and (B). 

(A) Securely Fastened. LFMC shall be securely fastened 
in place by an approved means within 300 mm (12 in.) of 
each box, cabinet, conduit body, or other conduit termina- 
tion and shall be supported and secured at intervals not to 
exceed 1.4 m (AV2 ft). 

Exception No. 1: Where LFMC is fished. 

Exception No. 2: Lengths not exceeding 900 mm (3 ft) at 
terminals where flexibility is necessary. 

Exception No. 3: Lengths not exceeding 1.8 m (6 ft) from a 
luminaire (fixture) terminal connection for tap conductors 
to luminaires (lighting fixtures), as permitted in 410.67(C). 

(B) Supports. Horizontal runs of LFMC supported by 
openings through framing members at intervals not greater 
than 1.4 m (AVi ft) and securely fastened within 300 mm 
(12 in.) of termination points shall be permitted. 

350.42 Couplings and Connectors. Angle connectors 
shall not be used for concealed raceway installations. 



350.22 Number of Conductors or Cables. 

(A) Metric Designators 16 through 103 (Trade Sizes Vi 
through 4). The number of conductors shall not exceed 
that permitted by the percentage fill specified in Table 1, 
Chapter 9. 

Cables shall be permitted to be installed where such use 
is permitted by the respective cable articles. The number of 
cables shall not exceed the allowable percentage fill speci- 
fied in Table 1, Chapter 9. 

(B) Metric Designator 12 (Trade Size %). The number of 
conductors shall not exceed that permitted in Table 348.22, 
"Fittings Outside Conduit" columns. 

350.24 Bends — How Made. Bends in conduit shall be 
made so that the conduit will not be damaged and the in- 
ternal diameter of the conduit will not be effectively re- 
duced. Bends shall be permitted to be made manually with- 
out auxiliary equipment. The radius of the curve to the 



350.56 Splices and Taps. Splices and taps shall be made 
in accordance with 300.15. 

350.60 Grounding and Bonding. Where used to connect 
equipment where flexibility is required, an equipment 
grounding conductor shall be installed. 

Where required or installed, equipment grounding con- 
ductors shall be installed in accordance with 250.134(B). 

Where required or installed, equipment bonding jump- 
ers shall be installed in accordance with 250.102. 

FPN: See 501.16(B), 502.16(B), and 503.16(B) for types 
of equipment grounding conductors. 



III. Construction Specifications 

350.120 Marking. LFMC shall be marked according to 
110.21. The trade size and other information required by 
the listing shall also be marked on the conduit. Conduit 
suitable for direct burial shall be so marked. 



NATIONAL ELECTRICAL CODE 



2002 Edition 



70-194 



ARTICLE 352 — RIGID NONMETALLIC CONDUIT: TYPE RNC 



ARTICLE 352 
Rigid Nonmetallic Conduit: Type RNC 



I. General 

352.1 Scope. This article covers the use, installation, and 
construction specifications for rigid nonmetallic conduit 
(RNC) and associated fittings. 

352.2 Definition. 

Rigid Nonmetallic Conduit (RNC). A nonmetallic race- 
way of circular cross section, with integral or associated 
couplings, connectors, and fittings for the installation of 
electrical conductors. 

352.6 Listing Requirements. RNC, factory elbows, and 
associated fittings shall be listed. 

II. Installation 

352.10 Uses Permitted. The use of RNC shall be permit- 
ted under the following conditions. 

FPN: Extreme cold may cause some nonmetallic conduits 
to become brittle and therefore more susceptible to damage 
from physical contact. 

(A) Concealed. In walls, floors, and ceilings. 

(B) Corrosive Influences. In locations subject to severe cor- 
rosive influences as covered in 300.6 and where subject to 
chemicals for which the materials are specifically approved. 

(C) Cinders. In cinder fill. 

(D) Wet Locations. In portions of dairies, laundries, can- 
neries, or other wet locations and in locations where walls 
are frequently washed, the entire conduit system including 
boxes and fittings used therewith shall be installed and 
equipped so as to prevent water from entering the conduit. 
All supports, bolts, straps, screws, and so forth, shall be of 
corrosion-resistant materials or be protected against corro- 
sion by approved corrosion-resistant materials. 

(E) Dry and Damp Locations. In dry and damp locations 
not prohibited by 352.12. 

(F) Exposed. For exposed work where not subject to 
physical damage if identified for such use. 

(G) Underground Installations. For underground installa- 
tions, see 300.5 and 300.50. Conduits listed for the purpose 
shall be permitted to be installed underground in continu- 
ous lengths from a reel. 



(H) Support of Conduit Bodies. Rigid nonmetallic con- 
duit shall be permitted to support nonmetallic conduit bod- 
ies not larger than the largest trade size of an entering 
raceway. The conduit bodies shall not contain devices or 
support luminaires (fixtures) or other equipment. 

352.12 Uses Not Permitted. RNC shall not be used in the 
following locations. 

(A) Hazardous (Classified) Locations. 

(1) In hazardous (classified) locations, except as permitted 
in 503.3(A), 504.20, 514.8, and 515.8 

(2) In Class I, Division 2 locations, except as permitted in 
501.4(B), Exception 

(B) Support of Luminaires (Fixtures). For the support of 
luminaires (fixtures) or other equipment not described in 
352.10(H). 

(C) Physical Damage. Where subject to physical damage 
unless identified for such use. 

(D) Ambient Temperatures. Where subject to ambient 
temperatures in excess of 50°C (122°F) unless listed other- 
wise. 

(E) Insulation Temperature Limitations. For conductors 
whose insulation temperature limitations would exceed 
those for which the conduit is listed. 

(F) Theaters and Similar Locations. In theaters and simi- 
lar locations, except as provided in Articles 518 and 520. 

352.20 Size. 

(A) Minimum. RNC smaller than metric designator 16 
(trade size Vi) shall not be used. 

(B) Maximum. RNC larger than metric designator 155 
(trade size 6) shall not be used. 

FPN: The trade sizes and metric designators are for iden- 
tification purposes only and do not relate to actual dimen- 
sions. See 300.1(C). 

352.22 Number of Conductors. The number of conduc- 
tors shall not exceed that permitted by the percentage fill 
specified in Table 1, Chapter 9. 

Cables shall be permitted to be installed where such use 
is permitted by the respective cable articles. The number of 
cables shall not exceed the allowable percentage fill speci- 
fied in Table 1, Chapter 9. 

352.24 Bends — How Made. Bends shall be made so that 
the conduit will not be damaged and the internal diameter 
of the conduit will not be effectively reduced. Field bends 
shall be made only with bending equipment identified for 



2002 Edition 



NATIONAL ELECTRICAL CODE 



ARTICLE 352 — RIGID NONMETALLIC CONDUIT: TYPE RNC 



70-195 



the purpose. The radius of the curve to the centerline of 
such bends shall not be less than shown in Table 344.24, 
column "Other Bends." 

352.26 Bends — Number in One Run. There shall not be 
more than the equivalent of four quarter bends (360 degrees 
total) between pull points, for example, conduit bodies and 
boxes. 

352.28 Trimming. All cut ends shall be trimmed inside 
and outside to remove rough edges. 

352.30 Securing and Supporting. RNC shall be installed 
as a complete system as provided in 300.18 and shall be 
fastened so that movement from thermal expansion or con- 
traction is permitted. RNC shall be securely fastened and 
supported in accordance with 352.30(A) and (B). 

(A) Securely Fastened. RNC shall be securely fastened 
within 900 mm (3 ft) of each outlet box, junction box, 
device box, conduit body, or other conduit termination. 
Conduit listed for securing at other than 900 mm (3 ft) 
shall be permitted to be installed in accordance with the 
listing. 

(B) Supports. RNC shall be supported as required in Table 
352.30(B). Conduit listed for support at spacings other than 
as shown in Table 352.30(B) shall be permitted to be in- 
stalled in accordance with the listing. Horizontal runs of 
RNC supported by openings through framing members at 
intervals not exceeding those in Table 352.30(B) and se- 
curely fastened within 900 mm (3 ft) of termination points 
shall be permitted. 

Table 352.30(B) Support of Rigid Nonmetallic 
Conduit (RNC) 







Maximum Spacing 


Conduit Size 


Between 


Supports 


Metric 








Designator 


Trade Size 


mm or m 


ft 


16-27 


Vi-\ 


900 mm 


3 


35-53 


VA-2 


1.5 m 


5 


63-78 


21/2-3 


1.8 m 


6 


91-129 


3 ] / 2 -5 


2.1 m 


7 


155 


6 


2.5 m 


8 



352.44 Expansion Fittings. Expansion fittings for RNC 
shall be provided to compensate for thermal expansion and 
contraction where the length change, in accordance with Table 
352.44(A) or (B), is expected to be 6 mm ( l A in.)or greater 
in a straight run between securely mounted items such as 
boxes, cabinets, elbows, or other conduit terminations. 



352.46 Bushings. Where a conduit enters a box, fitting, or 
other enclosure, a bushing or adapter shall be provided to 
protect the wire from abrasion unless the box, fitting, or 
enclosure design provides equivalent protection. 

FPN: See 300.4(F) for the protection of conductors 4 AWG 
and larger at bushings. 

352.48 Joints. All joints between lengths of conduit, and 
between conduit and couplings, fittings, and boxes, shall be 
made by an approved method. 

352.56 Splices and Taps. Splices and taps shall be made 
in accordance with 300.15. 

352.60 Grounding. Where equipment grounding is re- 
quired by Article 250, a separate equipment grounding con- 
ductor shall be installed in the conduit. 

Exception No. 1: As permitted in 250.134(B), Exception 
No. 2, for dc circuits and 250.134(B), Exception No. 1, for 
separately run equipment grounding conductors. 

Exception No. 2: Where the grounded conductor is used to 
ground equipment as permitted in 250.142. 

III. Construction Specifications 

352.100 Construction. RNC and fittings shall be com- 
posed of suitable nonmetallic material that is resistant to 
moisture and chemical atmospheres. For use above ground, 
it shall also be flame retardant, resistant to impact and 
crushing, resistant to distortion from heat under conditions 
likely to be encountered in service, and resistant to low 
temperature and sunlight effects. For use underground, the 
material shall be acceptably resistant to moisture and cor- 
rosive agents and shall be of sufficient strength to withstand 
abuse, such as by impact and crushing, in handling and 
during installation. Where intended for direct burial, with- 
out encasement in concrete, the material shall also be ca- 
pable of withstanding continued loading that is likely to be 
encountered after installation. 

352.120 Marking. Each length of RNC shall be clearly 
and durably marked at least every 3 m (10 ft) as required in 
the first sentence of 110.21. The type of material shall also 
be included in the marking unless it is visually identifiable. 
For conduit recognized for use above ground, these mark- 
ings shall be permanent. For conduit limited to under- 
ground use only, these markings shall be sufficiently du- 
rable to remain legible until the material is installed. 
Conduit shall be permitted to be surface marked to indicate 
special characteristics of the material. 

FPN: Examples of these markings include but are not lim- 
ited to "limited smoke" and "sunlight resistant." 



NATIONAL ELECTRICAL CODE 



2002 Edition 



70-196 



ARTICLE 352 — RIGID NONMETALLIC CONDUIT: TYPE RNC 



Table 352.44(A) Expansion Characteristics of PVC Rigid Nonmetallic Conduit Coefficient of Thermal Expansion = 
6.084 x 10~ 5 mm/mm/°C (3.38 x 10 -5 in./in./°F) 





Length Change of 




Length Change of 






Temperature 


PVC Conduit 


Temperature 


PVC Conduit 


Temperature 


Length Change of PVC 


Change (°C) 


(mm/m) 


Change (°F) 


(in./100 ft) 


Change (°F) 


Conduit (in./100 ft) 


5 


0.30 


5 


0.20 


105 


4.26 


10 


0.61 


10 


0.41 


110 


4.46 


15 


0.91 


15 


0.61 


115 


4.66 


20 


1.22 


20 


0.81 


120 


4.87 


25 


1.52 


25 


1.01 


125 


5.07 


30 


1.83 


30 


1.22 


130 


5.27 


35 


2.13 


35 


1.42 


135 


5.48 


40 


2.43 


40 


1.62 


140 


5.68 


45 


2.74 


45 


1.83 


145 


5.88 


50 


3.04 


50 


2.03 


150 


6.08 


55 


3.35 


55 


2.23 


155 


6.29 


60 


3.65 


60 


2.43 


160 


6.49 


65 


3.95 


65 


2.64 


165 


6.69 


70 


4.26 


70 


2.84 


170 


6.90 


75 


4.56 


75 


3.04 


175 


7.10 


80 


4.87 


80 


3.24 


180 


7.30 


85 


5.17 


85 


3.45 


185 


7.50 


90 


5.48 


90 


3.65 


190 


7.71 


95 


5.78 


95 


3.85 


195 


7.91 


100 


6.08 


100 


4.06 


200 


8.11 



Table 352.44(B) Expansion Characteristics of Reinforced Thermosetting Resin Conduit (RTRC) Coefficient of Thermal 
Expansion = 2.7 x 10 ~ 5 mm/mm/°C (1.5 x 10 -5 in./in./°F) 





Length Change of 




Length Change of 






Temperature 


RTRC Conduit 


Temperature 


RTRC Conduit 


Temperature Change 


Length Change of RTRC 


Change (°C) 


(mm/m) 


Change (°F) 


(in./100 ft) 


(°F) 


Conduit (in./100 ft) 


5 


0.14 


5 


0.09 


105 


1.89 


10 


0.27 


10 


0.18 


110 


1.98 


15 


0.41 


15 


0.27 


115 


2.07 


20 


0.54 


20 


0.36 


120 


2.16 


25 


0.68 


25 


0.45 


125 


2.25 


30 


0.81 


30 


0.54 


130 


2.34 


35 


0.95 


35 


0.63 


135 


2.43 


40 


1.08 


40 


0.72 


140 


2.52 


45 


1.22 


45 


0.81 


145 


2.61 


50 


1.35 


50 


0.90 


150 


2.70 


55 


1.49 


55 


0.99 


155 


2.79 


60 


1.62 


60 


1.08 


160 


2.88 


65 


1.76 


65 


1.17 


165 


2.97 


70 


1.89 


70 


1.26 


170 


3.06 


75 


2.03 


75 


1.35 


175 


3.15 


80 


2.16 


80 


1.44 


180 


3.24 


85 


2.30 


85 


1.53 


185 


3.33 


90 


2.43 


90 


1.62 


190 


3.42 


95 


2.57 


95 


1.71 


195 


3.51 


100 


2.70 


100 


1.80 


200 


3.60 



2002 Edition 



NATIONAL ELECTRICAL CODE 



ARTICLE 354 — NONMETALLIC UNDERGROUND CONDUIT WITH CONDUCTORS: TYPE NUCC 



70-197 



JVonte 

I. General 

354.1 Scope. This article covers the use, installation, and 
construction specifications for nonmetallic underground 
conduit with conductors (NUCC). 

354.2 Definition. 

Nonmetallic Underground Conduit with Conductors 

(NUCC). A factory assembly of conductors or cables inside 
a nonmetallic, smooth wall conduit with a circular cross 
section. 

354.6 Listing Requirements. NUCC and associated fit- 
tings shall be listed. 

II. Installation 

354.10 Uses Permitted. The use of NUCC and fittings 
shall be permitted in the following: 

(1) For direct burial underground installation (For mini- 
mum cover requirements, see Table 300.5 and Table 
300.50 under Rigid Nonmetallic Conduit.) 

(2) Encased or embedded in concrete 

(3) In cinder fill 

(4) In underground locations subject to severe corrosive 
influences as covered in 300.6 and where subject to 
chemicals for which the assembly is specifically 
approved 

354.12 Uses Not Permitted. NUCC shall not be used in 
the following: 

(1) In exposed locations 

(2) Inside buildings 

Exception: The conductor or the cable portion of the as- 
sembly, where suitable, shall be permitted to extend within 
the building for termination purposes in accordance with 
300.3. 

(3) In hazardous (classified) locations except as permitted 
by 503.3(A), 504.20, 514.8, and 515.8, and in Class I, 
Division 2 locations as permitted in 501.4(B)(3) 

354.20 Size. 

(A) Minimum. NUCC smaller than metric designator 16 
(trade size Vi) shall not be used. 



(B) Maximum. NUCC larger than metric designator 103 
(trade size 4) shall not be used. 

FPN: See 300.1(C) for the metric designators and trade 
sizes. These are for identification purposes only and do not 
relate to actual dimensions. 

354.22 Number of Conductors. The number of conduc- 
tors or cables shall not exceed that permitted by the per- 
centage fill in Table 1, Chapter 9. 

354.24 Bends — How Made. Bends shall be manually 
made so that the conduit will not be damaged and the in- 
ternal diameter of the conduit will not be effectively re- 
duced. The radius of the curve of the centerline of such 
bends shall not be less than shown in Table 354.24. 



Table 354.24 Minimum Bending Radius for Nonmetallic 
Underground Conduit with Conductors (NUCC) 



Conduit Size 


Minimum Bend 


ing Radius 


Metric 








Designator 


Trade Size 


mm 


in. 


16 


' '/2 


250 


10 


21 


3 /4 


300 


12 


27 


1 


350 


14 


35 


l'/4 


450 


18 


41 


l'/2 


500 


20 


53 


2 


650 


26 


63 


2'/2 


900 


36 


78 


3 


1200 


48 


103 


4 


1500 


60 



354.26 Bends — Number in One Run. There shall not be 
more than the equivalent of four quarter bends (360 degrees 
total) between termination points. 

354.28 Trimming. For termination, the conduit shall be 
trimmed away from the conductors or cables using an ap- 
proved method that will not damage the conductor or cable 
insulation or jacket. All conduit ends shall be trimmed in- 
side and out to remove rough edges. 

354.46 Bushings. Where the NUCC enters a box, fitting, 
or other enclosure, a bushing or adapter shall be provided 
to protect the conductor or cable from abrasion unless the 
design of the box, fitting, or enclosure provides equivalent 
protection. 

FPN: See 300.4(F) for the protection of conductors size 4 
AWG or larger. 

354.48 Joints. All joints between conduit, fittings, and 
boxes shall be made by an approved method. 



NATIONAL ELECTRICAL CODE 



2002 Edition 



70-198 



ARTICLE 356 — LIQUIDTIGHT FLEXIBLE NONMETALLIC CONDUIT: TYPE LFNC 



354.50 Conductor Terminations. All terminations be- 
tween the conductors or cables and equipment shall be 
made by an approved method for that type of conductor or 
cable. 

354.56 Splices and Taps. Splices and taps shall be made 
in junction boxes or other enclosures. 

354.60 Grounding. Where equipment grounding is re- 
quired by Article 250, an assembly containing a separate 
equipment grounding conductor shall be used. 

III. Construction Specifications 
354.100 Construction. 

(A) General. NUCC is an assembly that is provided in 
continuous lengths shipped in a coil, reel, or carton. 

(B) Nonmetallic Underground Conduit. The nonmetallic 
underground conduit shall be listed and composed of a ma- 
terial that is resistant to moisture and corrosive agents. It 
shall also be capable of being supplied on reels without 
damage or distortion and shall be of sufficient strength to 
withstand abuse, such as impact or crushing, in handling 
and during installation without damage to conduit or con- 
ductors. 

(C) Conductors and Cables. Conductors and cables used 
in NUCC shall be listed and shall comply with 310.8(C). 
Conductors of different systems shall be installed in accor- 
dance with 300.3(C). 

(D) Conductor Fill. The maximum number of conductors 
or cables in NUCC shall not exceed that permitted by the 
percentage fill in Table 1, Chapter 9. 

354.120 Marking. NUCC shall be clearly and durably 
marked at least every 3.05 m (10 ft) as required by 110.21. 
The type of conduit material shall also be included in the 
marking. 

Identification of conductors or cables used in the assem- 
bly shall be provided on a tag attached to each end of the 
assembly or to the side of a reel. Enclosed conductors or 
cables shall be marked in accordance with 310.11. 



ARTICLE 356 

Liquidtight Flexible Nonmetallic 

Conduit: Type LFNC 



I. General 

356.1 Scope. This article covers the use, installation, and 
construction specifications for liquidtight flexible nonme- 
tallic conduit (LFNC) and associated fittings. 



356.2 Definition. 

Liquidtight Flexible Nonmetallic Conduit (LFNC). A 

raceway of circular cross section of various types as fol- 
lows: 

(1) A smooth seamless inner core and cover bonded to- 
gether and having one or more reinforcement layers 
betv/een the core and covers, designated as Type 
LFNC-A 

(2) A smooth inner surface with integral reinforcement 
within the conduit wall, designated as Type LFNC-B 

(3) A corrugated internal and external surface without in- 
tegral reinforcement within the conduit wall, desig- 
nated as LFNC-C. 

LFNC is flame resistant and with fittings and is ap- 
proved for the installation of electrical conductors. 

FPN: FNMC is an alternative designation for LFNC. 

356.6 Listing Requirements. LFNC and associated fit- 
tings shall be listed. 

II. Installation 

356.10 Uses Permitted. LFNC shall be permitted to be 
used in exposed or concealed locations for the following 
purposes: 

FPN: Extreme cold may cause some types of nonmetallic 
conduits to become brittle and therefore more susceptible to 
damage from physical contact. 

(1) Where flexibility is required for installation, operation, 
or maintenance 

(2) Where protection of the contained conductors is re- 
quired from vapors, liquids, or solids 

(3) For outdoor locations where listed and marked as suit- 
able for the purpose 

(4) For direct burial where listed and marked for the pur- 
pose 

(5) Type LFNC-B shall be permitted to be installed in 
lengths longer than 1.8 m (6 ft) where secured in ac- 
cordance with 356.30 

(6) Type LFNC-B as a listed manufactured prewired as- 
sembly, metric designator 16 through 27 (trade size ] /i 
through 1) conduit 

356.12 Uses Not Permitted. LFNC shall not be used as 
follows: 

(1) Where subject to physical damage 

(2) Where any combination of ambient and conductor tem- 
peratures is in excess of that for which the LFNC is 
approved 

(3) In lengths longer than 1.8 m (6 ft), except as permitted 
by 356.10(5) or where a longer length is approved as 
essential for a required degree of flexibility 



2002 Edition 



NATIONAL ELECTRICAL CODE 



ARTICLE 356 — LIQUIDTIGHT FLEXIBLE NONMETALLIC CONDUIT: TYPE LFNC 



70-199 



(4) Where voltage of the contained conductors is in excess 
of 600 volts, nominal 

356.20 Size. 

(A) Minimum. LFNC smaller than metric designator 16 
(trade size Vi) shall not be used unless permitted in 
356.20(A)(1) through (3) for metric designator 12 (trade 
size 3 /s). 

(1) For enclosing the leads of motors as permitted in 
430.145(B) 

(2) In lengths not exceeding 1.8 m (6 ft ) as part of a listed 
assembly for tap connections to luminaires (lighting 
fixtures) as required in 410.67(C), or for utilization 
equipment 

(3) For electric sign conductors in accordance with 
600.32(A) 

(B) Maximum. LFNC larger than metric designator 103 
(trade size 4) shall not be used. 

FPN: See 300.1(C) for the metric designators and trade 
sizes. These are for identification purposes only and do not 
relate to actual dimensions. 

356.22 Number of Conductors. The number of conduc- 
tors shall not exceed that permitted by the percentage fill 
specified in Table 1, Chapter 9. 

Cables shall be permitted to be installed where such use 
is permitted by the respective cable articles. The number of 
cables shall not exceed the allowable percentage fill speci- 
fied in Table 1, Chapter 9. 

356.24 Bends — How Made. Bends in conduit shall be 
made so that the conduit is not damaged and the internal 
diameter of the conduit is not effectively reduced. Bends 
shall be permitted to be made manually without auxiliary 
equipment. The radius of the curve to the centerline of any 
bend shall not be less than shown in Table 344.24 using the 
column "Other Bends." 

356.26 Bends — Number in One Run. There shall not be 
more than the equivalent of four quarter bends (360 degrees 
total) between pull points, for example, conduit bodies and 
boxes. 



356.28 Trimming. All cut ends of conduit shall 
trimmed inside and outside to remove rough edges. 



be 



356.30 Securing and Supporting. Type LFNC-B shall be 
securely fastened and supported in accordance with one of 
the following: 



(1) The conduit shall be securely fastened at intervals not 
exceeding 900 mm (3 ft) and within 300 mm (12 in.) 
on each side of every outlet box, junction box, cabinet, 
or fitting. 

(2) Securing or supporting of the conduit shall not be re- 
quired where it is fished, installed in lengths not ex- 
ceeding 900 mm (3 ft) at terminals where flexibility is 
required, or installed in lengths not exceeding 1.8 m 
(6 ft) from a luminaire (fixture) terminal connection for 
tap conductors to luminaires (lighting fixtures) permit- 
ted in 410.67(C). 

(3) Horizontal runs of LFNC supported by openings 
through framing members at intervals not exceeding 
900 mm (3 ft) and securely fastened within 300 mm 
(12 in.) of termination points shall be permitted. 

356.42 Couplings and Connectors. Angle connectors 
shall not be used for concealed raceway installations. 

356.56 Splices and Taps. Splices and taps shall be made 
in accordance with 300.15. 

356.60 Grounding and Bonding. Where used to connect 
equipment where flexibility is required, an equipment 
grounding conductor shall be installed. 

Where required or installed, equipment grounding con- 
ductors shall be installed in accordance with 250.134(B). 

Where required or installed, equipment bonding jump- 
ers shall be installed in accordance with 250.102. 

III. Construction Specifications 

356.100 Construction. LFNC-B as a prewired manufac- 
tured assembly shall be provided in continuous lengths ca- 
pable of being shipped in a coil, reel, or carton without 
damage. 

356.120 Marking. LFNC shall be marked at least every 
600 mm (2 ft) in accordance with 110.21. The marking 
shall include a type designation in accordance with 356.2 
and the trade size. Conduit that is intended for outdoor use 
or direct burial shall be marked. 

The type, size, and quantity of conductors used in 
prewired manufactured assemblies shall be identified by 
means of a printed tag or label attached to each end of the 
manufactured assembly and either the carton, coil, or reel. 
The enclosed conductors shall be marked in accordance 
with 310.11. 



NATIONAL ELECTRICAL CODE 



2002 Edition 



70-200 



ARTICLE 358 — ELECTRICAL METALLIC TUBING: TYPE EMT 



Electrical Metallic T\ibing: TYpe EMT 



I. General 

358.1 Scope. This article covers the use, installation, and 
construction specifications for electrical metallic tubing 
(EMT) and associated fittings. 

358.2 Definition. 

Electrical Metallic Tubing (EMT). An unthreaded thin- 
wall raceway of circular cross section designed for the 
physical protection and routing of conductors and cables 
and for use as an equipment grounding conductor when 
installed utilizing appropriate fittings. EMT is generally 
made of steel (ferrous) with protective coatings or alumi- 
num (nonferrous). 

358.6 Listing Requirements. EMT, factory elbows, and 
associated fittings shall be listed. 

II. Installation 
358.10 Uses Permitted. 

(A) Exposed and Concealed. The use of EMT shall be 
permitted for both exposed and concealed work. 

(B) Corrosion Protection. Ferrous or nonferrous EMT, el- 
bows, couplings, and fittings shall be permitted to be installed 
in concrete, in direct contact with the earth, or in areas subject 
to severe corrosive influences where protected by corrosion 
protection and judged suitable for the condition. 

(C) Wet Locations. All supports, bolts, straps, screws, and 
so forth shall be of corrosion-resistant materials or pro- 
tected against corrosion by corrosion-resistant materials. 

FPN: See 300.6 for protection against corrosion. 

358.12 Uses Not Permitted. EMT shall not be used under 
the following conditions: 

(1) Where, during installation or afterward, it will be sub- 
ject to severe physical damage 

(2) Where protected from corrosion solely by enamel 

(3) In cinder concrete or cinder fill where subject to per- 
manent moisture unless protected on all sides by a 
layer of noncinder concrete at least 50 mm (2 in.) thick 
or unless the tubing is at least 450 mm (18 in.) under 
the fill 

(4) In any hazardous (classified) location except as permit- 
ted by 502.4, 503.3, and 504.20 



(5) For the support of luminaires (fixtures) or other equip- 
ment except conduit bodies no larger than the largest 
trade size of the tubing 

(6) Where practicable, dissimilar metals in contact any- 
where in the system shall be avoided to eliminate the 
possibility of galvanic action 

Exception: Aluminum fittings and enclosures shall be per- 
mitted to be used with steel EMT where not subject to 
severe corrosive influences. 

358.20 Size. 

(A) Minimum. EMT smaller than metric designator 16 
(trade size Vi) shall not be used. 

Exception: For enclosing the leads of motors as permitted 
in 430.145(B). 

(B) Maximum. The maximum size of EMT shall be met- 
ric designator 103 (trade size 4). 

FPN: See 300.1(C) for the metric designators and trade 
sizes. These are for identification purposes only and do not 
relate to actual dimensions. 

358.22 Number of Conductors. The number of conduc- 
tors shall not exceed that permitted by the percentage fill 
specified in Table 1, Chapter 9. 

Cables shall be permitted to be installed where such use 
is permitted by the respective cable articles. The number of 
cables shall not exceed the allowable percentage fill speci- 
fied in Table 1, Chapter 9. 

358.24 Bends — How Made. Bends shall be made so that 
the tubing is not damaged and the internal diameter of the 
tubing is not effectively reduced. The radius of the curve of 
any field bend to the centerline of the conduit shall not be 
less than shown in Table 344.24 for one-shot and full shoe 
benders. 

358.26 Bends — Number in One Run. There shall not be 
more than the equivalent of four quarter bends (360 degrees 
total) between pull points, for example, conduit bodies and 
boxes. 

358.28 Reaming and Threading. 

(A) Reaming. All cut ends of EMT shall be reamed or 
otherwise finished to remove rough edges. 

(B) Threading. EMT shall not be threaded. 

Exception: EMT with factory threaded integral couplings 
complying with 358.100. 

358.30 Securing and Supporting. EMT shall be installed 
as a complete system as provided in Article 300 and shall 



2002 Edition 



NATIONAL ELECTRICAL CODE 



ARTICLE 360 — FLEXIBLE METALLIC TUBING: TYPE FMT 



70-201 



be securely fastened in place and supported in accordance 
with 358.30(A) and (B). 

(A) Securely Fastened. EMT shall be securely fastened 
in place at least every 3 m (10 ft). In addition, each EMT 
run between termination points shall be securely fas- 
tened within 900 mm (3 ft) of each outlet box, junction 
box, device box, cabinet, conduit body, or other tubing 
termination. 

Exception No. 1: Fastening of unbroken lengths shall be 
permitted to be increased to a distance of 1.5 m (5 ft) where 
structural members do not readily permit fastening within 
900 mm (3 ft). 

Exception No. 2: For concealed work in finished buildings 
or prefinished wall panels where such securing is imprac- 
ticable, unbroken lengths (without coupling) of EMT shall 
be permitted to be fished. 

(B) Supports. Horizontal runs of EMT supported by open- 
ings through framing members at intervals not greater than 
3 m (10 ft) and securely fastened within 900 mm (3 ft) of 
termination points shall be permitted. 

358.42 Couplings and Connectors. Couplings and con- 
nectors used with EMT shall be made up tight. Where bur- 
ied in masonry or concrete, they shall be concretetight type. 
Where installed in wet locations, they shall be of the rain- 
tight type. 

358.56 Splices and Taps. Splices and taps shall be made 
in accordance with 300.15. 

358.60 Grounding. EMT shall be permitted as an equip- 
ment grounding conductor. 

III. Construction Specifications 

358.100 Construction. Factory-threaded integral cou- 
plings shall be permitted. Where EMT with a threaded in- 
tegral coupling is used, threads for both the tubing and 
coupling shall be factory-made. The coupling and EMT 
threads shall be designed so as to prevent bending of the 
tubing at any part of the thread. 

358.120 Marking. EMT shall be clearly and durably 
marked at least every 3 m (10 ft) as required in the first 
sentence of 110.21. 






I. General 

360.1 Scope. This article covers the use, installation, and 
construction specifications for flexible metallic tubing 
(FMT) and associated fittings. 

360.2 Definition. 

Flexible Metallic Tubing (FMT). A raceway that is circu- 
lar in cross section, flexible, metallic, and liquidtight with- 
out a nonmetallic jacket. 

360.6 Listing Requirements. FMT and associated fittings 
shall be listed. 

II. Installation 

360.10 Uses Permitted. FMT shall be permitted to be used 
for branch circuits as follows: 

(1) In dry locations 

(2) Where concealed 

(3) In accessible locations 

(4) For system voltages of 1000 volts maximum 

360.12 Uses Not Permitted. FMT shall not be used as 
follows: 

(1) In hoistways 

(2) In storage battery rooms 

(3) In hazardous (classified) locations unless otherwise 
permitted under other articles in this Code 

(4) Under ground for direct earth burial, or embedded in 
poured concrete or aggregate 

(5) Where subject to physical damage 

(6) In lengths over 1.8 m (6 ft) 

360.20 Size. 

(A) Minimum. FMT smaller than metric designator 16 
(trade size Vi) shall not be used. 

Exception No. 1: FMT of metric designator 12 (trade size 
3 /s) shall be permitted to be installed in accordance with 
300.22(B) and (C). 

Exception No. 2: FMT of metric designator 12 (trade size 
3 /s) shall be permitted in lengths not in excess of 1.8 m (6 ft) 
as part of an approved assembly or for luminaires (lighting 
fixtures). See 410.67(C). 

(B) Maximum. The maximum size of FMT shall be metric 
designator 21 (trade size 3 A). 



NATIONAL ELECTRICAL CODE 



2002 Edition 



70-202 



ARTICLE 362 — ELECTRICAL NONMETALLIC TUBING: TYPE ENT 



FPN: See 300.1(C) for the metric designators and trade 
sizes. These are for identification purposes only and do not 
relate to actual dimensions. 

360.22 Number of Conductors. 

(A) FMT — Metric Designators 16 and 21 (Trade Sizes 

Vi and 3 A). The number of conductors in metric designators 
16 (trade size Vi) and 21 (trade size 3 A) shall not exceed 
that permitted by the percentage fill specified in Table 1, 
Chapter 9. 

Cables shall be permitted to be installed where such use 
is permitted by the respective cable articles. The number of 
cables shall not exceed the allowable percentage fill speci- 
fied in Table 1, Chapter 9. 

(B) FMT — Metric Designator 12 (Trade Size 3 /s). The 
number of conductors in metric designator 12 (trade size 
3 /s) shall not exceed that permitted in Table 348.22. 

360.24 Bends. 

(A) Infrequent Flexing Use. Where FMT may be infre- 
quently flexed in service after installation, the radii of 
bends measured to the inside of the bend shall not be less 
than specified in Table 360.24(A). 

Table 360.24(A) Minimum Radii for Flexing Use 



Metric 
Designator 



Trade Size 



Minimum Radii for 
Flexing Use 

mm in. 



12 


y 8 


25.4 


10 


16 


Vi 


317.5 


12'/2 


21 


3 /4 


444.5 


17'/ 2 



(B) Fixed Bends. Where FMT is bent for installation pur- 
poses and is not flexed or bent as required by use after 
installation, the radii of bends measured to the inside of the 
bend shall not be less than specified in Table 360.24(B). 

Table 360.24(B) Minimum Radii for Fixed Bends 

Minimum Radii for 
Fixed Bends 



Metric 
Designator 



Trade Size 



mm 



in. 



12 


Vs 


88.9 


3Vi 


16 


Vl 


101.6 


4 


21 


3 /4 


127.0 


5 



360.40 Boxes and Fittings. Fittings shall effectively close 
any openings in the connection. 



360.56 Splices and Taps. Splices and taps shall be made 
in accordance with 300.15. 

360.60 Grounding. FMT shall be permitted as an equip- 
ment grounding conductor where installed in accordance 
with 250.118(8). 

III. Construction Specifications 

360.120 Marking. FMT shall be marked according to 
110.21. 



ARTICLE 362 

Electrical Nonmetallic Hibing: 

Type ENT 



I. General 

362.1 Scope. This article covers the use, installation, and 
construction specifications for electrical nonmetallic tubing 
(ENT) and associated fittings. 

362.2 Definition. 

Electrical Nonmetallic Tubing (ENT). A nonmetallic pli- 
able corrugated raceway of circular cross section with inte- 
gral or associated couplings, connectors, and fittings for the 
installation of electric conductors. ENT is composed of a 
material that is resistant to moisture and chemical atmo- 
spheres and is flame retardant. 

A pliable raceway is a raceway that can be bent by hand 
with a reasonable force, but without other assistance. 

362.6 Listing Requirements. ENT and associated fittings 
shall be listed. 

II. Installation 

362.10 Uses Permitted. For the purpose of this article, the 
first floor of a building shall be that floor that has 50 per- 
cent or more of the exterior wall surface area level with or 
above finished grade. One additional level that is the first 
level and not designed for human habitation and used only 
for vehicle parking, storage, or similar use shall be permit- 
ted. The use of ENT and fittings shall be permitted in the 
following: 

(1) In any building not exceeding three floors above grade 

a. For exposed work, where not prohibited by 362.12 

b. Concealed within walls, floors, and ceilings 

(2) In any building exceeding three floors above grade, 
ENT shall be concealed within walls, floors, and ceil- 



2002 Edition 



NATIONAL ELECTRICAL CODE 



ARTICLE 362 — ELECTRICAL NONMETALLIC TUBING: TYPE ENT 



70-203 



ings where the walls, floors, and ceilings provide a 
thermal barrier of material that has at least a 15-minute 
finish rating as identified in listings of fire-rated assem- 
blies. The 15-minute-finish-rated thermal barrier shall 
be permitted to be used for combustible or noncombus- 
tible walls, floors, and ceilings. 

Exception: Where a fire sprinkler system(s) is installed in 
accordance with NFPA 13-1999, Standard for the Installa- 
tion of Sprinkler Systems, on all floors, ENT is permitted to 
be used within walls, floors, and ceilings, exposed or con- 
cealed, in buildings exceeding three floors above grade. 

FPN: A finish rating is established for assemblies contain- 
ing combustible (wood) supports. The finish rating is de- 
fined as the time at which the wood stud or wood joist 
reaches an average temperature rise of 121°C (250°F) or an 
individual temperature of 163°C (325°F) as measured on 
the plane of the wood nearest the fire. A finish rating is not 
intended to represent a rating for a membrane ceiling. 

(3) In locations subject to severe corrosive influences as 
covered in 300.6 and where subject to chemicals for 
which the materials are specifically approved. 

(4) In concealed, dry, and damp locations not prohibited by 
362.12. 

(5) Above suspended ceilings where the suspended ceil- 
ings provide a thermal barrier of material that has at 
least a 15-minute finish rating as identified in listings of 
fire-rated assemblies, except as permitted in 
362.10(l)(a). 

Exception: Where a fire sprinkler system(s) is installed in 
accordance with NFPA 13-1999, Standard for the Installa- 
tion of Sprinkler Systems, on all floors, ENT is permitted to 
be used within walls, floors, and ceilings, exposed or con- 
cealed, in buildings exceeding three floors above grade. 

(6) Encased in poured concrete, or embedded in a concrete 
slab on grade where ENT is placed on sand or ap- 
proved screenings, provided fittings identified for this 
purpose are used for connections. 

(7) For wet locations indoors as permitted in this section or 
in a concrete slab on or below grade, with fittings listed 
for the purpose. 

(8) Metric designator 16 through 27 (trade size l A through 
1) as listed manufactured prewired assembly. 

FPN: Extreme cold may cause some types of nonmetallic 
conduits to become brittle and therefore more susceptible to 
damage from physical contact. 

362.12 Uses Not Permitted. ENT shall not be used in the 
following: 

(1) In hazardous (classified) locations, except as permit- 
ted by 504.20 and 505.15(A)(1) 

(2) For the support of luminaires (fixtures) and other 
equipment 



(3) Where subject to ambient temperatures in excess of 
50°C (122°F) unless listed otherwise 

(4) For conductors whose insulation temperature limita- 
tions would exceed those for which the tubing is listed 

(5) For direct earth burial 

(6) Where the voltage is over 600 volts 

(7) In exposed locations, except as permitted by 
362.10(1), 362.10(5), and 362.10(7) 

(8) In theaters and similar locations, except as provided in 
Articles 518 and 520 

(9) Where exposed to the direct rays of the sun, unless 
identified as sunlight resistant 

(10) Where subject to physical damage 

362.20 Size. 

(A) Minimum. ENT smaller than metric designator 16 
(trade size Vi) shall not be used. 

(B) Maximum. ENT larger than metric designator 53 
(trade size 2) shall not be used. 

FPN: See 300.1(C) for the metric designators and trade 
sizes. These are for identification purposes only and do not 
relate to actual dimensions. 

362.22 Number of Conductors. The number of conduc- 
tors shall not exceed that permitted by the percentage fill in 
Table 1, Chapter 9. 

Cables shall be permitted to be installed where such use 
is permitted by the respective cable articles. The number of 
cables shall not exceed the allowable percentage fill speci- 
fied in Table 1, Chapter 9. 

362.24 Bends — How Made. Bends shall be made so that 
the tubing will not be damaged and that the internal diam- 
eter of the tubing will not be effectively reduced. Bends 
shall be permitted to be made manually without auxiliary 
equipment, and the radius of the curve to the centerline of 
such bends shall not be less than shown in Table 344.24 
using the column "Other Bends." 

362.26 Bends — Number in One Run. There shall not be 
more than the equivalent of four quarter bends (360 degrees 
total) between pull points, for example, conduit bodies and 
boxes. 

362.28 Trimming. All cut ends shall be trimmed inside 
and outside to remove rough edges. 

362.30 Securing and Supporting. ENT shall be installed 
as a complete system as provided in Article 300 and shall 
be securely fastened in place and supported in accordance 
with 362.30(A) and (B). 



NATIONAL ELECTRICAL CODE 



2002 Edition 



70-204 



ARTICLE 366 — AUXILIARY GUTTERS 



(A) Securely Fastened. ENT shall be securely fastened at 
intervals not exceeding 900 mm (3 ft). In addition, ENT 
shall be securely fastened in place within 900 mm (3 ft) of 
each outlet box, device box, junction box, cabinet, or fitting 
where it terminates. 

Exception: Lengths not exceeding a distance of 1.8 m (6 ft) 
from a luminaire (fixture) terminal connection for tap con- 
nections to lighting luminaires (fixtures) shall be permitted 
without being secured. 

(B) Supports. Horizontal runs of ENT supported by open- 
ings in framing members at intervals not exceeding 900 
mm (3 ft) and securely fastened within 900 mm (3 ft) of 
termination points shall be permitted. 

362.46 Bushings. Where a tubing enters a box, fitting, or 
other enclosure, a bushing or adapter shall be provided to 
protect the wire from abrasion unless the box, fitting, or 
enclosure design provides equivalent protection. 

FPN: See 300.4(F) for the protection of conductors size 4 
AWG or larger. 

362.48 Joints. All joints between lengths of tubing and 
between tubing and couplings, fittings, and boxes shall be 
by an approved method. 

362.56 Splices and Taps. Splices and taps shall be made 
only in accordance with 300.15. 

FPN: See Article 314 for rules on the installation and use 
of boxes and conduit bodies. 

362.60 Grounding. Where equipment grounding is re- 
quired by Article 250, a separate equipment grounding con- 
ductor shall be installed in the raceway. 

III. Construction Specifications 

362.100 Construction. ENT shall be made of material that 
does not exceed the ignitibility, flammability, smoke gen- 
eration, and toxicity characteristics of rigid (nonplasticized) 
polyvinyl chloride. 

ENT, as a prewired manufactured assembly, shall be 
provided in continuous lengths capable of being shipped in 
a coil, reel, or carton without damage. 

362.120 Marking. ENT shall be clearly and durably 
marked at least every 3 m (10 ft) as required in the first 
sentence of 110.21. The type of material shall also be in- 
cluded in the marking. Marking for limited smoke shall be 
permitted on the tubing that has limited smoke-producing 
characteristics. 

The type, size, and quantity of conductors used in 
prewired manufactured assemblies shall be identified by 



means of a printed tag or label attached to each end of the 
manufactured assembly and either the carton, coil, or reel. 
The enclosed conductors shall be marked in accordance 
with 310.11. 



ARTIGLE:366 
Auxiliary Gutters 



366.1 Scope. This article covers the use, installation and 
construction requirements of metal auxiliary gutters and 
nonmetallic auxiliary gutters and associated fittings. 

366.2 Use. Auxiliary gutters shall be permitted to supple- 
ment wiring spaces at meter centers, distribution centers, 
switchboards, and similar points of wiring systems and may 
enclose conductors or busbars but shall not be used to en- 
close switches, overcurrent devices, appliances, or other 
similar equipment. 

366.3 Extension Beyond Equipment. An auxiliary gutter 
shall not extend a greater distance than 9 m (30 ft) beyond 
the equipment that it supplements. 

Exception: As permitted in 620.35 for elevators, an auxil- 
iary gutter shall be permitted to extend a distance greater 
than 9 m (30 ft) beyond the equipment that it supplements. 

FPN: For wireways, see Articles 376 and 378. For 
bus ways, see Article 368. 

366.4 Supports. 

(A) Sheet Metal Auxiliary Gutters. Sheet metal auxiliary 
gutters shall be supported throughout their entire length at 
intervals not exceeding 1.5 m (5 ft). 

(B) Nonmetallic Auxiliary Gutters. Nonmetallic auxil- 
iary gutters shall be supported at intervals not to exceed 
900 mm (3 ft) and at each end or joint, unless listed for 
other support intervals. In no case shall the distance be- 
tween supports exceed 3 m (10 ft). 

366.5 Covers. Covers shall be securely fastened to the gutter. 

366.6 Number of Conductors. 

(A) Sheet Metal Auxiliary Gutters. The sum of the cross- 
sectional areas of all contained conductors at any cross 
section of a sheet metal auxiliary gutter shall not exceed 
20 percent of the interior cross-sectional area of the sheet 
metal auxiliary gutter. The derating factors in 310.15(B)(2)(a) 
shall be applied only where the number of current-carrying 
conductors, including neutral conductors classified as 



2002 Edition 



NATIONAL ELECTRICAL CODE 



ARTICLE 366 — AUXILIARY GUTTERS 



70-205 



current-carrying under the provisions of 310.15(B)(4), ex- 
ceeds 30. Conductors for signaling circuits or controller 
conductors between a motor and its starter and used only 
for starting duty shall not be considered as current-carrying 
conductors. 

(B) Nonmetallic Auxiliary Gutters. The sum of cross- 
sectional areas of all contained conductors at any cross 
section of the nonmetallic auxiliary gutter shall not exceed 
20 percent of the interior cross-sectional area of the non- 
metallic auxiliary gutter. 

366.7 Ampacity of Conductors. 

(A) Sheet Metal Auxiliary Gutters. Where the number of 
current-carrying conductors contained in the sheet metal 
auxiliary gutter is 30 or less, the correction factors specified 
in 310.15(B)(2)(a) shall not apply. The current carried con- 
tinuously in bare copper bars in sheet metal auxiliary gut- 
ters shall not exceed 1.55 amperes/mm 2 (1000 amperes/in. 2 ) 
of cross section of the conductor. For aluminum bars, the cur- 
rent carried continuously shall not exceed 1.09 amperes/mm 2 
(700 amperes/in. 2 ) of cross section of the conductor. 

(B) Nonmetallic Auxiliary Gutters. The derating factors 
specified in 310.15(B)(2)(a) shall be applicable to the 
current-carrying conductors in the nonmetallic auxiliary 
gutter. 

366.8 Clearance of Bare Live Parts. Bare conductors 
shall be securely and rigidly supported so that the minimum 
clearance between bare current-carrying metal parts of dif- 
ferent potential mounted on the same surface will not be 
less than 50 mm (2 in.), nor less than 25 mm (1 in.) for 
parts that are held free in the air. A clearance not less than 
25 mm (1 in.) shall be secured between bare current- 
carrying metal parts and any metal surface. Adequate pro- 
visions shall be made for the expansion and contraction of 
busbars. 

366.9 Splices and Taps. Splices and taps shall comply 
with 366.9(A) through (D). 

(A) Within Gutters. Splices or taps shall be permitted 
within gutters where they are accessible by means of re- 
movable covers or doors. The conductors, including splices 
and taps, shall not fill the gutter to more than 75 percent of 
its area. 

(B) Bare Conductors. Taps from bare conductors shall 
leave the gutter opposite their terminal connections, and 
conductors shall not be brought in contact with uninsulated 
current-carrying parts of different potential. 

(C) Suitably Identified. All taps shall be suitably identi- 
fied at the gutter as to the circuit or equipment that they 
supply. 



(D) Overcurrent Protection. Tap connections from con- 
ductors in auxiliary gutters shall be provided with overcur- 
rent protection as required in 240.21. 

366.10 Construction and Installation. Auxiliary gutters 
shall comply with 366.10(A) through (F). 

(A) Electrical and Mechanical Continuity. Gutters shall 
be constructed and installed so that adequate electrical and 
mechanical continuity of the complete system is secured. 

(B) Substantial Construction. Gutters shall be of substan- 
tial construction and shall provide a complete enclosure for 
the contained conductors. All surfaces, both interior and 
exterior, shall be suitably protected from corrosion. Corner 
joints shall be made tight, and where the assembly is held 
together by rivets, bolts, or screws, such fasteners shall be 
spaced not more than 300 mm (12 in.) apart. 

(C) Smooth Rounded Edges. Suitable bushings, shields, 
or fittings having smooth, rounded edges shall be provided 
where conductors pass between gutters, through partitions, 
around bends, between gutters and cabinets or junction 
boxes, and at other locations where necessary to prevent 
abrasion of the insulation of the conductors. 

(D) Deflected Insulated Conductors. Where insulated 
conductors are deflected within an auxiliary gutter, either at 
the ends or where conduits, fittings, or other raceways or 
cables enter or leave the gutter, or where the direction of 
the gutter is deflected greater than 30 degrees, dimensions 
corresponding to 312.6 shall apply. 

(E) Indoor and Outdoor Use. 

(1) Sheet Metal Auxiliary Gutters. Sheet metal auxiliary 
gutters installed in wet locations shall be suitable for such 
locations. 

(2) Nonmetallic Auxiliary Gutters. 

(a) Nonmetallic auxiliary gutters installed outdoors 
shall comply with the following: 

(1) Be listed and marked as suitable for exposure to sun- 
light 

(2) Be listed and marked as suitable for use in wet loca- 
tions 

(3) Be listed for the maximum ambient temperature of the 
installation, and marked for the installed conductor in- 
sulation temperature rating 

(4) Have expansion fittings installed where the expected 
length change due to expansion and contraction due to 
temperature change is more than 6 mm (0.25 in.) 

(b) Nonmetallic auxiliary gutters installed indoors shall 
comply with the following: 



NATIONAL ELECTRICAL CODE 



2002 Edition 



70-206 



ARTICLE 368 — BUSWAYS 



(1) Be listed for the maximum ambient temperature of the 
installation and marked for the installed conductor in- 
sulation temperature rating 

(2) Have expansion fittings installed where expected length 
change, due to expansion and contraction due to tem- 
perature change, is more than 6 mm (0.25 in.) 

FPN: Extreme cold may cause nonmetallic auxiliary gutter 
to become brittle and therefore more susceptible to damage 
from physical contact. 

(F) Grounding. Grounding shall be in accordance with the 
provisions of Article 250. 



(1) Where subject to severe physical damage or corrosive 
vapors 

(2) In hoistways 

(3) In any hazardous (classified) location, unless specifi- 
cally approved for such use 

FPN: See 501.4(B). 

(4) Outdoors or in wet or damp locations unless identified 
for such use 

Lighting busway and trolley busway shall not be in- 
stalled less than 2.5 m (8 ft) above the floor or working 
platform unless provided with a cover identified for the 
purpose. 



ARTICLE 368 
Busways 



368.5 Support. Busways shall be securely supported at 
intervals not exceeding 1.5 m (5 ft) unless otherwise de- 
signed and marked. 



I. General Requirements 

368.1 Scope. This article covers service-entrance, feeder, 
and branch-circuit busways and associated fittings. 

368.2 Definition. 

Busway. A grounded metal enclosure containing factory- 
mounted, bare or insulated conductors, which are usually 
copper or aluminum bars, rods, or tubes. 

FPN: For cablebus, refer to Article 370. 

368.4 Use. 

(A) Uses Permitted. Busways shall be permitted to be in- 
stalled where they are located as follows: 

(1) Located in the open and are visible, except as permitted 
in 368.6, or 

(2) Installed behind access panels, provided the busways 
are totally enclosed, of nonventilating-type construc- 
tion, and installed so that the joints between sections 
and at fittings are accessible for maintenance purposes. 
Where installed behind access panels, means of access 
shall be provided, and the following conditions shall be 
met: 

a. The space behind the access panels shall not be used 
for air-handling purposes, or 

b. Where the space behind the access panels is used 
for environmental air, other than ducts and plenums, 
there shall be no provisions for plug-in connections, 
and the conductors shall be insulated. 

(B) Uses Not Permitted. Busways shall not be installed as 
follows: 



368.6 Through Walls and Floors. 

(A) Walls. Unbroken lengths of busway shall be permitted 
to be extended through dry walls. 

(B) Floors. Floor penetrations shall comply with (1) and (2): 

(1) Busways shall be permitted to be extended vertically 
through dry floors if totally enclosed (unventilated) 
where passing through and for a minimum distance of 
1.8 m (6 ft) above the floor to provide adequate protec- 
tion from physical damage. 

(2) In other than industrial establishments, where a vertical 
riser penetrates two or more dry floors, a minimum 
100 mm (4 in.) high curb shall be installed around all 
floor openings for riser busways to prevent liquids from 
entering the opening. The curb shall be installed within 
300 mm (12 in.) of the floor opening. Electrical equip- 
ment shall be located so that it will not be damaged by 
liquids that are retained by the curb. 

FPN: See 300.21 for information concerning the spread of 
fire or products of combustion. 



368.7 Dead Ends. A dead end of a busway shall be closed. 

368.8 Branches from Busways. Branches from busways 
shall be permitted to be made in accordance with 368.8(A), 
(B), and (C). 

(A) General. Branches from busways shall be made in 
accordance with Articles 320, 330, 332, 342, 344, 348, 350, 
352, 356, 358, 362, 368, 384, 386, and 388. Where a sepa- 
rate equipment grounding conductor is used, connection of 
the equipment grounding conductor to the busway shall 
comply with 250.8 and 250.12. 



2002 Edition 



NATIONAL ELECTRICAL CODE 



ARTICLE 368 — BUSWAYS 



70-207 



(B) Cord and Cable Assemblies. Suitable cord and cable 
assemblies approved for extra-hard usage or hard usage and 
listed bus drop cable shall be permitted as branches from 
busways for the connection of portable equipment or the 
connection of stationary equipment to facilitate their inter- 
change in accordance with 400.7 and 400.8 and the follow- 
ing conditions: 

(1) The cord or cable shall be attached to the building by 
an approved means. 

(2) The length of the cord or cable from a busway plug-in 
device to a suitable tension take-up support device shall 
not exceed 1.8 m (6 ft). 

Exception: In industrial establishments only, where the 
conditions of maintenance and supervision ensure that only 
qualified persons service the installation, lengths exceeding 
1.8 m (6 ft) shall be permitted between the busway plug-in 
device and the tension take-up support device where the 
cord or cable is supported at intervals not exceeding 2.5 m 
(8 ft). 

(3) The cord or cable shall be installed as a vertical riser 
from the tension take-up support device to the equip- 
ment served. 

(4) Strain relief cable grips shall be provided for the cord 
or cable at the busway plug-in device and equipment 
terminations. 

(C) Branches from Trolley-Type Busways. Suitable cord 
and cable assemblies approved for extra-hard usage or hard 
usage and listed bus drop cable shall be permitted as 
branches from trolley-type busways for the connection of 
movable equipment in accordance with 400.7 and 400.8. 

368.9 Overcurrent Protection. Overcurrent protection 
shall be provided in accordance with 368.10 through 
368.13. 

368.10 Rating of Overcurrent Protection — Feeders. A 

busway shall be protected against overcurrent in accor- 
dance with the allowable current rating of the busway. 

Exception No. 1: The applicable provisions of 240.4 shall 
be permitted. 

Exception No. 2: Where used as transformer secondary 
ties, the provisions of 450.6(A)(3) shall be permitted. 

368.11 Reduction in Ampacity Size of Busway. Over- 
current protection shall be required where busways are re- 
duced in ampacity. 

Exception: For industrial establishments only, omission of 
overcurrent protection shall be permitted at points where 
busways are reduced in ampacity, provided that the length 
of the busway having the smaller ampacity does not exceed 
15 m (50 ft) and has an ampacity at least equal to one-third 



the rating or setting of the overcurrent device next back on 
the line, and provided that such busway is free from contact 
with combustible material. 

368.12 Feeder or Branch Circuits. Where a busway is 
used as a feeder, devices or plug-in connections for tapping 
off feeder or branch circuits from the busway shall contain 
the overcurrent devices required for the protection of the 
feeder or branch circuits. The plug-in device shall consist 
of an externally operable circuit breaker or an externally 
operable fusible switch. Where such devices are mounted 
out of reach and contain disconnecting means, suitable 
means such as ropes, chains, or sticks shall be provided for 
operating the disconnecting means from the floor. 

Exception No. 1: As permitted in 240.21. 

Exception No. 2: For fixed or semifixed luminaires (light- 
ing fixtures), where the branch-circuit overcurrent device is 
part of the luminaire (fixture) cord plug on cord-connected 
luminaires (fixtures). 

Exception No. 3: Where luminaires (fixtures) without cords 
are plugged directly into the busway and the overcurrent 
device is mounted on the luminaire (fixture). 

368.13 Rating of Overcurrent Protection — Branch 
Circuits. A busway used as a branch circuit shall be pro- 
tected against overcurrent in accordance with 210.20. 
Where so used, the circuit shall comply with the applicable 
requirements of Articles 210, 430, and 440. 

368.15 Marking. Busways shall be marked with the volt- 
age and current rating for which they are designed, and 
with the manufacturer's name or trademark in such manner 
as to be visible after installation. 

II. Requirements for Over 600 Volts, Nominal 

368.21 Identification. Each bus run shall be provided with 
a permanent nameplate on which the following information 
shall be provided: 

(1) Rated voltage 

(2) Rated continuous current; if bus is forced-cooled, both 
the normal forced-cooled rating and the self-cooled 
(not forced-cooled) rating for the same temperature rise 
shall be given 

(3) Rated frequency 

(4) Rated impulse withstand voltage 

(5) Rated 60-Hz withstand voltage (dry) 

(6) Rated momentary current 

(7) Manufacturer's name or trademark 

FPN: See ANSI C37.23-1987 (R1991), Guide for Metal- 
Enclosed Bus and Calculating Losses in Isolated-Phase 



NATIONAL ELECTRICAL CODE 



2002 Edition 



70-208 



ARTICLE 370 — CABLEBUS 



Bus, for construction and testing requirements for metal- 
enclosed buses. 



368.22 Grounding. Metal-enclosed bus shall be grounded 
in accordance with Article 250. 

368.23 Adjacent and Supporting Structures. Metal- 
enclosed busways shall be installed so that temperature rise 
from induced circulating currents in any adjacent metallic 
parts will not be hazardous to personnel or constitute a fire 
hazard. 



link enclosures shall be interlocked to prevent access to 
energized parts. 

368.30 Wiring 600 Volts or Less, Nominal. Secondary 
control devices and wiring that are provided as part of the 
metal-enclosed bus run shall be insulated by fire-retardant 
barriers from all primary circuit elements with the excep- 
tion of short lengths of wire, such as at instrument trans- 
former terminals. 



368.24 Neutral. Neutral bus, where required, shall be 
sized to carry all neutral load current, including harmonic 
currents, and shall have adequate momentary and short- 
circuit rating consistent with system requirements. 

368.25 Barriers and Seals. Bus runs that have sections 
located both inside and outside of buildings shall have a 
vapor seal at the building wall to prevent interchange of air 
between indoor and outdoor sections. 

Exception: Vapor seals shall not be required in forced- 
cooled bus. 

Fire barriers shall be provided where fire walls, floors, 
or ceilings are penetrated. 

FPN: See 300.21 for information concerning the spread of 
fire or products of combustion. 

368.26 Drain Facilities. Drain plugs, filter drains, or simi- 
lar methods shall be provided to remove condensed mois- 
ture from low points in bus run. 

368.27 Ventilated Bus Enclosures. Ventilated bus enclo- 
sures shall be installed in accordance with Article 110, Part 
III, and 490.24. 

368.28 Terminations and Connections. Where bus enclo- 
sures terminate at machines cooled by flammable gas, seal-off 
bushings, baffles, or other means shall be provided to prevent 
accumulation of flammable gas in the bus enclosures. 

Flexible or expansion connections shall be provided in 
long, straight runs of bus to allow for temperature expan- 
sion or contraction, or where the bus run crosses building 
vibration insulation joints. 

All conductor termination and connection hardware shall 
be accessible for installation, connection, and maintenance. 

368.29 Switches. Switching devices or disconnecting links 
provided in the bus run shall have the same momentary 
rating as the bus. Disconnecting links shall be plainly 
marked to be removable only when bus is de-energized. 
Switching devices that are not load-break shall be inter- 
locked to prevent operation under load, and disconnecting 



ARTICLE 370 
Cablebus 



370.1 Scope. This article covers the use and installation 
requirements of cablebus and associated fittings. 

370.2 Definition. 

Cablebus. An assembly of insulated conductors with fit- 
tings and conductor terminations in a completely enclosed, 
ventilated protective metal housing. Cablebus is ordinarily 
assembled at the point of installation from the components 
furnished or specified by the manufacturer in accordance 
with instructions for the specific job. This assembly is de- 
signed to carry fault current and to withstand the magnetic 
forces of such current. 

370.3 Use. Approved cablebus shall be permitted at any 
voltage or current for which spaced conductors are rated 
and shall be installed for exposed work only, except as 
permitted in 370.6. Cablebus installed outdoors or in cor- 
rosive, wet, or damp locations shall be identified for such 
use. Cablebus shall not be installed in hoistways or hazard- 
ous (classified) locations unless specifically approved for 
such use. Cablebus shall be permitted to be used for branch 
circuits, feeders, and services. 

Cablebus framework, where bonded as required by Ar- 
ticle 250, shall be permitted as the equipment grounding 
conductor for branch circuits and feeders. 

370.4 Conductors. 

(A) Types of Conductors. The current-carrying conduc- 
tors in cablebus shall have an insulation rating of 75°C 
(167°F) or higher of an approved type and suitable for the 
application in accordance with Articles 310 and 490. 

(B) Ampacity of Conductors. The ampacity of conduc- 
tors in cablebus shall be in accordance with Tables 310.17 
and 310.19, or with Tables 310.69 and 310.70 for installa- 
tions over 600 volts. 



2002 Edition 



NATIONAL ELECTRICAL CODE 



ARTICLE 372 — CELLULAR CONCRETE FLOOR RACEWAYS 



70-209 



(C) Size and Number of Conductors. The size and num- 
ber of conductors shall be that for which the cablebus is 
designed, and in no case smaller than 1/0 AWG. 

(D) Conductor Supports. The insulated conductors shall 
be supported on blocks or other mounting means designed 
for the purpose. 

The individual conductors in a cablebus shall be sup- 
ported at intervals not greater than 900 mm (3 ft) for hori- 
zontal runs and 450 mm (IV2 ft) for vertical runs. Vertical 
and horizontal spacing between supported conductors shall 
not be less than one conductor diameter at the points of 
support. 

370.5 Overcurrent Protection. Cablebus shall be pro- 
tected against overcurrent in accordance with the allowable 
ampacity of the cablebus conductors in accordance with 
240.4. 

Exception: Overcurrent protection shall be permitted in 
accordance with 240.100 and 240.101 for over 600 volts, 
nominal. 



(1) Changes in horizontal or vertical direction of the run 

(2) Dead ends 

(3) Terminations in or on connected apparatus or equip- 
ment or the enclosures for such equipment 

(4) Additional physical protection where required, such as 
guards where subject to severe physical damage 

370.8 Conductor Terminations. Approved terminating 
means shall be used for connections to cablebus conductors. 

370.9 Grounding. A cablebus installation shall be 
grounded and bonded in accordance with Article 250, ex- 
cluding 250.86, Exception No. 2. 

370.10 Marking. Each section of cablebus shall be 
marked with the manufacturer's name or trade designation 
and the maximum diameter, number, voltage rating, and 
ampacity of the conductors to be installed. Markings shall 
be located so as to be visible after installation. 



370.6 Support and Extension Through Walls and 
Floors. 

(A) Support. Cablebus shall be securely supported at in- 
tervals not exceeding 3.7 m (12 ft). 

Exception: Where spans longer than 3.7 m (12 ft) are re- 
quired, the structure shall be specifically designed for the 
required span length. 

(B) Transversely Routed. Cablebus shall be permitted to 
extend transversely through partitions or walls, other than 
fire walls, provided the section within the wall is continu- 
ous, protected against physical damage, and unventilated. 

(C) Through Dry Floors and Platforms. Except where 
firestops are required, cablebus shall be permitted to extend 
vertically through dry floors and platforms, provided the 
cablebus is totally enclosed at the point where it passes 
through the floor or platform and for a distance of 1.8 m 
(6 ft) above the floor or platform. 

(D) Through Floors and Platforms in Wet Locations. 

Except where firestops are required, cablebus shall be per- 
mitted to extend vertically through floors and platforms in 
wet locations where (1) there are curbs or other suitable 
means to prevent waterflow through the floor or platform 
opening, and (2) where the cablebus is totally enclosed at 
the point where it passes through the floor or platform and 
for a distance of 1.8 m (6 ft) above the floor or platform. 

370.7 Fittings. A cablebus system shall include approved 
fittings for the following: 



ARTICLE 372 
Cellular Concrete Floor Raceways 



372.1 Scope. This article covers cellular concrete floor 
raceways, the hollow spaces in floors constructed of precast 
cellular concrete slabs, together with suitable metal fittings 
designed to provide access to the floor cells. 

372.2 Definitions. 

Cell. A single, enclosed tubular space in a floor made of 
precast cellular concrete slabs, the direction of the cell be- 
ing parallel to the direction of the floor member. 

Header. Transverse metal raceways for electric conductors, 
providing access to predetermined cells of a precast cellular 
concrete floor, thereby permitting the installation of electric 
conductors from a distribution center to the floor cells. 

372.3 Other Articles. Cellular concrete floor raceways 
shall comply with the applicable provisions of Article 300. 

372.4 Uses Not Permitted. Conductors shall not be in- 
stalled in precast cellular concrete floor raceways as fol- 
lows: 

(1) Where subject to corrosive vapor 

(2) In any hazardous (classified) locations except as per- 
mitted by 504.20, and in Class I, Division 2 locations 
as permitted in 501.4(B)(3) 



NATIONAL ELECTRICAL CODE 



2002 Edition 



70-210 



ARTICLE 374 — CELLULAR METAL FLOOR RACEWAYS 



(3) In commercial garages, other than for supplying ceiling 
outlets or extensions to the area below the floor but not 
above 

FPN: See 300.8 for installation of conductors with other 
systems. 

372.5 Header. The header shall be installed in a straight 
line at right angles to the cells. The header shall be me- 
chanically secured to the top of the precast cellular concrete 
floor. The end joints shall be closed by a metal closure 
fitting and sealed against the entrance of concrete. The 
header shall be electrically continuous throughout its entire 
length and shall be electrically bonded to the enclosure of 
the distribution center. 

372.6 Connection to Cabinets and Other Enclosures. 

Connections from headers to cabinets and other enclosures 
shall be made by means of listed metal raceways and listed 
fittings. 

372.7 Junction Boxes. Junction boxes shall be leveled to 
the floor grade and sealed against the free entrance of water 
or concrete. Junction boxes shall be of metal and shall be 
mechanically and electrically continuous with the header. 

372.8 Markers. A suitable number of markers shall be 
installed for the future location of cells. 

372.9 Inserts. Inserts shall be leveled and sealed against 
the entrance of concrete. Inserts shall be of metal and shall 
be fitted with grounded-type receptacles. A grounding con- 
ductor shall connect the insert receptacles to a positive 
ground connection provided on the header. Where cutting 
through the cell wall for setting inserts or other purposes 
(such as providing access openings between header and 
cells), chips and other dirt shall not be allowed to remain in 
the raceway, and the tool used shall be designed so as to 
prevent the tool from entering the cell and damaging the 
conductors. 

372.10 Size of Conductors. No conductor larger than 1/0 
AWG shall be installed, except by special permission. 

372.11 Maximum Number of Conductors. The com- 
bined cross-sectional area of all conductors or cables shall 
not exceed 40 percent of the cross-sectional area of the cell 
or header. 

372.12 Splices and Taps. Splices and taps shall be made 
only in header access units or junction boxes. 

For the purposes of this section, so-called loop wiring 
(continuous unbroken conductor connecting the individual 
outlets) shall not be considered to be a splice or tap. 



372.13 Discontinued Outlets. When an outlet is aban- 
doned, discontinued, or removed, the sections of circuit 
conductors supplying the outlet shall be removed from the 
raceway. No splices or reinsulated conductors, such as 
would be the case of abandoned outlets on loop wiring, 
shall be allowed in raceways. 



ARTICLE 374 
Cellular Metal Floor Raceways 

374.1 Scope. This article covers the use and installation 
requirements for cellular metal floor raceways. 

374.2 Definitions. 

Cellular Metal Floor Raceway. The hollow spaces of cel- 
lular metal floors, together with suitable fittings, that may 
be approved as enclosures for electric conductors. 

Cell. A single, enclosed tubular space in a cellular metal 
floor member, the axis of the cell being parallel to the axis 
of the metal floor member. 

Header. A transverse raceway for electric conductors, pro- 
viding access to predetermined cells of a cellular metal 
floor, thereby permitting the installation of electric conduc- 
tors from a distribution center to the cells. 

374.3 Uses Not Permitted. Conductors shall not be in- 
stalled in cellular metal floor raceways as follows: 

(1) Where subject to corrosive vapor 

(2) In any hazardous (classified) location except as permit- 
ted by 504.20, and in Class I, Division 2 locations as 
permitted in 501.4(B)(3) 

(3) In commercial garages, other than for supplying ceiling 
outlets or extensions to the area below the floor but not 
above 

FPN: See 300.8 for installation of conductors with other 
systems. 

I. Installation 

374.4 Size of Conductors. No conductor larger than 1/0 
AWG shall be installed, except by special permission. 

374.5 Maximum Number of Conductors in Raceway. 

The combined cross-sectional area of all conductors or 
cables shall not exceed 40 percent of the interior cross- 
sectional area of the cell or header. 

374.6 Splices and Taps. Splices and taps shall be made 
only in header access units or junction boxes. 



2002 Edition 



NATIONAL ELECTRICAL CODE 



ARTICLE 376 — METAL WIREWAYS 



70-21 



For the purposes of this section, so-called loop wiring 
(continuous unbroken conductor connecting the individual 
outlets) shall not be considered to be a splice or tap. 

374.7 Discontinued Outlets. When an outlet is aban- 
doned, discontinued, or removed, the sections of circuit 
conductors supplying the outlet shall be removed from the 
raceway. No splices or reinsulated conductors, such as 
would be the case with abandoned outlets on loop wiring, 
shall be allowed in raceways. 

374.8 Markers. A suitable number of markers shall be 
installed for locating cells in the future. 

374.9 Junction Boxes. Junction boxes shall be leveled to 
the floor grade and sealed against the free entrance of water 
or concrete. Junction boxes used with these raceways shall 
be of metal and shall be electrically continuous with the 
raceway. 

374.10 Inserts. Inserts shall be leveled to the floor grade 
and sealed against the entrance of concrete. Inserts shall be 
of metal and shall be electrically continuous with the race- 
way. In cutting through the cell wall and setting inserts, 
chips and other dirt shall not be allowed to remain in the 
raceway, and tools shall be used that are designed to pre- 
vent the tool from entering the cell and damaging the 
conductors. 

374.11 Connection to Cabinets and Extensions from 
Cells. Connections between raceways and distribution cen- 
ters and wall outlets shall be made by means of flexible 
metal conduit where not installed in concrete, rigid metal 
conduit, intermediate metal conduit, electrical metallic tub- 
ing, or approved fittings. Where there are provisions for the 
termination of an equipment grounding conductor, nonme- 
tallic conduit, electrical nonmetallic tubing, or liquidtight 
flexible nonmetallic conduit where not installed in concrete 
shall be permitted. 

II. Construction Specifications 

374.12 General. Cellular metal floor raceways shall be 
constructed so that adequate electrical and mechanical con- 
tinuity of the complete system will be secured. They shall 
provide a complete enclosure for the conductors. The inte- 
rior surfaces shall be free from burrs and sharp edges, and 
surfaces over which conductors are drawn shall be smooth. 
Suitable bushings or fittings having smooth rounded edges 
shall be provided where conductors pass. 



ARTICLE 376 
Metal Wireways 



I. General 



376.1 Scope. This article covers the use, installation, and 
construction specifications for metal wireways and associ- 
ated fittings. 

376.2 Definition. 

Metal Wireways. Sheet metal troughs with hinged or re- 
movable covers for housing and protecting electric wires 
and cable and in which conductors are laid in place after 
the wireway has been installed as a complete system. 

II. Installation 

376.10 Uses Permitted. The use of metal wireways shall 
be permitted in the following: 

(1) For exposed work 

(2) In concealed spaces as permitted in 376.10(4) 

(3) In hazardous (classified) locations as permitted by 
501.4(B) for Class I, Division 2 locations; 502.4(B) for 
Class II, Division 2 locations; and 504.20 for intrinsi- 
cally safe wiring. Where installed in wet locations, 
wireways shall be listed for the purpose. 

(4) As extensions to pass transversely through walls if the 
length passing through the wall is unbroken. Access to 
the conductors shall be maintained on both sides of the 
wall. 

376.12 Uses Not Permitted. Metal wireways shall not be 
used in the following: 

(1) Where subject to severe physical damage 

(2) Where subject to severe corrosive environments 

376.21 Size of Conductors. No conductor larger than that 
for which the wireway is designed shall be installed in any 
wireway. 

376.22 Number of Conductors. The sum of the cross- 
sectional areas of all contained conductors at any cross 
section of a wireway shall not exceed 20 percent of the 
interior cross-sectional area of the wireway. The derating 
factors in 310.15(B)(2)(a) shall be applied only where the 
number of current-carrying conductors, including neutral 
conductors classified as current-carrying under the provi- 
sions of 310.15(B)(4), exceeds 30. Conductors for signaling 
circuits or controller conductors between a motor and its 
starter and used only for starting duty shall not be consid- 
ered as current-carrying conductors. 



NATIONAL ELECTRICAL CODE 



2002 Edition 



70-212 



ARTICLE 378 — NONMETALLIC WIREWAYS 



376.23 Insulated Conductors. Insulated conductors in- 
stalled in a metallic wireway shall comply with 376.23(A) 
and (B). 

(A) Deflected Insulated Conductors. Where insulated 
conductors are deflected within a metallic wireway, either 
at the ends or where conduits, fittings, or other raceways or 
cables enter or leave the metallic wireway, or where the 
direction of the metallic wireway is deflected greater than 
30 degrees, dimensions corresponding to 312.6(A) shall 
apply. 

(B) Metallic Wireways Used as Pullboxes. Where insu- 
lated conductors 4 AWG or larger are pulled through a 
wireway, the distance between raceway and cable entries 
enclosing the same conductor shall not be less than that 
required in 314.28(A)(1) for straight pulls and 
314.28(A)(2) for angle pulls. 

376.30 Securing and Supporting. Metal wireways shall 
be supported in accordance with 376.30(A) and (B). 

(A) Horizontal Support. Wireways shall be supported 
where run horizontally at each end and at intervals not to 
exceed 1.5 m (5 ft) or for individual lengths longer than 1.5 
m (5 ft) at each end or joint, unless listed for other support 
intervals. The distance between supports shall not exceed 
3 m (10 ft). 

(B) Vertical Support. Vertical runs of wireways shall be 
securely supported at intervals not exceeding 4.5 m (15 ft) 
and shall not have more than one joint between supports. 
Adjoining wireway sections shall be securely fastened to- 
gether to provide a rigid joint. 

376.56 Splices and Taps. Splices and taps shall be permit- 
ted within a wireway provided they are accessible. The 
conductors, including splices and taps, shall not fill the 
wireway to more than 75 percent of its area at that point. 

376.58 Dead Ends. Dead ends of metal wireways shall be 
closed. 

376.70 Extensions from Metal Wireways. Extensions 
from wireways shall be made with cord pendants installed 
in accordance with 400.10 or any wiring method in Chapter 
3 that includes a means for equipment grounding. Where a 
separate equipment grounding conductor is employed, con- 
nection of the equipment grounding conductors in the wir- 
ing method to the wireway shall comply with 250.8 and 
250.12. 

III. Construction Specifications 

376.120 Marking. Metal wireways shall be marked so that 
their manufacturer's name or trademark will be visible after 
installation. 



ARTICLE 378 
Nonmetallic Wireways 



I. General 



378.1 Scope. This article covers the use, installation, and 
construction specifications for nonmetallic wireways and 
associated fittings. 

378.2 Definition. 

Nonmetallic Wireways. Flame retardant, nonmetallic 
troughs with removable covers for housing and protecting 
electric wires and cables in which conductors are laid in 
place after the wireway has been installed as a complete 
system. 

378.3 Other Articles. Installations of nonmetallic wire- 
ways shall comply with the applicable provisions of Article 
300. 

378.6 Listing Requirements. Nonmetallic wireways and 
associated fittings shall be listed. 

II. Installation 

378.10 Uses Permitted. The use of nonmetallic wireways 
shall be permitted in the following: 

(1) Only for exposed work, except as permitted in 
378.10(4). 

(2) Where subject to corrosive environments where identi- 
fied for the use. 

(3) In wet locations where listed for the purpose. 

FPN: Extreme cold may cause nonmetallic wireways to 
become brittle and therefore more susceptible to damage 
from physical contact. 

(4) As extensions to pass transversely through walls if the 
length passing through the wall is unbroken. Access to 
the conductors shall be maintained on both sides of the 
wall. 

378.12 Uses Not Permitted. Nonmetallic wireways shall 
not be used in the following: 

(1) Where subject to physical damage 

(2) In any hazardous (classified) location, except as permit- 
ted in 504.20 

(3) Where exposed to sunlight unless listed and marked as 
suitable for the purpose 

(4) Where subject to ambient temperatures other than those 
for which nonmetallic wireway is listed 



2002 Edition 



NATIONAL ELECTRICAL CODE 



ARTICLE 380 — MULTIOUTLET ASSEMBLY 



70-213 



(5) For conductors whose insulation temperature limita- 
tions would exceed those for which the nonmetallic 
wireway is listed 

378.21 Size of Conductors. No conductor larger than that 
for which the nonmetallic wireway is designed shall be 
installed in any nonmetallic wireway. 



378.44 Expansion Fittings. Expansion fittings for nonme- 
tallic wireway shall be provided to compensate for thermal 
expansion and contraction where the length change is ex- 
pected to be 6 mm (0.25 in.) or greater in a straight run. 

FPN: See Table 352.44(A) for expansion characteristics of 
PVC rigid nonmetallic conduit. The expansion characteris- 
tics of PVC nonmetallic wireway are identical. 



378.22 Number of Conductors. The sum of cross- 
sectional areas of all contained conductors at any cross 
section of the nonmetallic wireway shall not exceed 20 per- 
cent of the interior cross-sectional area of the nonmetallic 
wireway. Conductors for signaling circuits or controller 
conductors between a motor and its starter and used only 
for starting duty shall not be considered as current-carrying 
conductors. 

The derating factors specified in 310.15(B)(2)(a) shall 
be applicable to the current-carrying conductors up to and 
including the 20 percent fill specified above. 

378.23 Insulated Conductors. Insulated conductors in- 
stalled in a nonmetallic wireway shall comply with 
378.23(A) and (B). 

(A) Deflected Insulated Conductors. Where insulated 
conductors are deflected within a nonmetallic wireway, ei- 
ther at the ends or where conduits, fittings, or other race- 
ways or cables enter or leave the nonmetallic wireway, or 
where the direction of the nonmetallic wireway is deflected 
greater than 30 degrees, dimensions corresponding to 
312.6(A) shall apply. 

(B) Nonmetallic Wire ways Used as Pull Boxes. Where 
insulated conductors 4 AWG or larger are pulled through a 
wireway, the distance between raceway and cable entries 
enclosing the same conductor shall not be less than that 
required in 314.28(A)(1) for straight pulls and in 
314.28(A)(2) for angle pulls. 

378.30 Securing and Supporting. Nonmetallic wireway 
shall be supported in accordance with 378.30(A) and (B). 

(A) Horizontal Support. Nonmetallic wireways shall be 
supported where run horizontally at intervals not to exceed 
900 mm (3 ft), and at each end or joint, unless listed for 
other support intervals. In no case shall the distance be- 
tween supports exceed 3 m (10 ft). 

(B) Vertical Support. Vertical runs of nonmetallic wire- 
way shall be securely supported at intervals not exceeding 
1.2 m (4 ft), unless listed for other support intervals, and 
shall not have more than one joint between supports. Ad- 
joining nonmetallic wireway sections shall be securely fas- 
tened together to provide a rigid joint. 



378.56 Splices and Taps. Splices and taps shall be permit- 
ted within a nonmetallic wireway, provided they are acces- 
sible. The conductors, including splices and taps, shall not 
fill the nonmetallic wireway to more than 75 percent of its 
area at that point. 

378.58 Dead Ends. Dead ends of nonmetallic wireway 
shall be closed using listed fittings. 

378.60 Grounding. Where equipment grounding is re- 
quired by Article 250, a separate equipment grounding con- 
ductor shall be installed in the nonmetallic wireway. A 
separate equipment grounding conductor shall not be re- 
quired where the grounded conductor is used to ground 
equipment as permitted in 250.142. 

378.70 Extensions from Nonmetallic Wireways. Ex- 
tensions from nonmetallic wireway shall be made with cord 
pendants or any wiring method of Chapter 3. A separate 
equipment grounding conductor shall be installed in, or an 
equipment grounding connection shall be made to, any of 
the wiring methods used for the extension. 

III. Construction Specifications 

378.120 Marking. Nonmetallic wireways shall be marked 
so that the manufacturer's name or trademark and interior 
cross-sectional area in square inches shall be visible after 
installation. Marking for limited smoke shall be permitted 
on the nonmetallic wireways that have limited smoke- 
producing characteristics. 



ARTICLE 380 
; ; Multioutlet Assembly 

380.1 Scope. This article covers the use and installation 
requirements for multioutlet assemblies. 

380.2 Use. 

(A) Permitted. The use of a multioutlet assembly shall be 
permitted in dry locations. 



NATIONAL ELECTRICAL CODE 



2002 Edition 



70-214 



ARTICLE 382 — NONMETALLIC EXTENSIONS 



(B) Not Permitted. A multioutlet assembly shall not be 
installed as follows: 

(1) Where concealed, except that it shall be permissible to 
surround the back and sides of a metal multioutlet as- 
sembly by the building finish or recess a nonmetallic 
multioutlet assembly in a baseboard 

(2) Where subject to severe physical damage 

(3) Where the voltage is 300 volts or more between con- 
ductors unless the assembly is of metal having a thick- 
ness of not less than 1.02 mm (0.040 in.) 

(4) Where subject to corrosive vapors 

(5) In hoistways 

(6) In any hazardous (classified) locations except Class I, 
Division 2 locations as permitted in 501.4(B)(3) 

380.3 Metal Multioutlet Assembly Through Dry Parti- 
tions. It shall be permissible to extend a metal multioutlet 
assembly through (not run within) dry partitions if arrange- 
ments are made for removing the cap or cover on all ex- 
posed portions and no outlet is located within the partitions. 



the building is occupied for residential or office purposes 
and does not exceed three floors above grade. 

FPN No. 1: See 310.10 for temperature limitation of con- 
ductors. 

FPN No. 2: See 362.10 for definition of first floor. 

382.12 Uses Not Permitted. Nonmetallic extensions shall 
not be used as follows: 

(1) In unfinished basements, attics, or roof spaces 

(2) Where the voltage between conductors exceeds 150 
volts for nonmetallic surface extension and 300 volts 
for aerial cable 

(3) Where subject to corrosive vapors 

(4) Where run through a floor or partition, or outside the 
room in which it originates 

382.15 Exposed. One or more extensions shall be permit- 
ted to be run in any direction from an existing outlet, but 
not on the floor or within 50 mm (2 in.) from the floor. 



ARTICLE 382 
Nonmetallic Extensions 



I. General 



382.1 Scope. This article covers the use, installation, and 
construction specifications for nonmetallic extensions. 

382.2 Definition. 

Nonmetallic Extension. An assembly of two insulated 
conductors within a nonmetallic jacket or an extruded ther- 
moplastic covering. The classification includes surface ex- 
tensions intended for mounting directly on the surface of 
walls or ceilings. 

II. Installation 

382.10 Uses Permitted. Nonmetallic extensions shall be 
permitted only where all the conditions in 382.10(A), (B), 
and (C) are met. 

(A) From an Existing Outlet. The extension is from an 
existing outlet on a 15- or 20-ampere branch circuit. 

(B) Exposed and in a Dry Location. The extension is run 
exposed and in a dry location. 

(C) Residential or Offices. For nonmetallic surface exten- 
sions mounted directly on the surface of walls or ceilings, 



382.26 Bends. A bend that reduces the normal spacing be- 
tween the conductors shall be covered with a cap to protect 
the assembly from physical damage. 

382.30 Securing and Supporting. Nonmetallic surface 
extensions shall be secured in place by approved means at 
intervals not exceeding 200 mm (8 in.), with an allowance 
for 300 mm (12 in.) to the first fastening where the connec- 
tion to the supplying outlet is by means of an attachment 
plug. There shall be at least one fastening between each two 
adjacent outlets supplied. An extension shall be attached to 
only woodwork or plaster finish and shall not be in contact 
with any metal work or other conductive material other 
than with metal plates on receptacles. 

382.40 Boxes and Fittings. Each run shall terminate in a 
fitting that covers the end of the assembly. All fittings and 
devices shall be of a type identified for the use. 

382.56 Splices and Taps. Extensions shall consist of a 
continuous unbroken length of the assembly, without 
splices, and without exposed conductors between fittings. 
Taps shall be permitted where approved fittings completely 
covering the tap connections are used. Aerial cable and its 
tap connectors shall be provided with an approved means 
for polarization. Receptacle-type tap connectors shall be of 
the locking type. 



2002 Edition 



NATIONAL ELECTRICAL CODE 



ARTICLE 384 — STRUT-TYPE CHANNEL RACEWAY 



70-215 



Table 384.22 Channel Size and Inside Diameter Area 



ARTICLE 384 

I. General 

384.1 Scope. This article covers the use, installation, and 
construction specifications of strut-type channel raceway. 

384.2 Definition. 

Strut-Type Channel Raceway. A metallic raceway that is 
intended to be mounted to the surface of or suspended from 
a structure, with associated accessories for the installation 
of electrical conductors. 

384.6 Listing Requirements. Strut-type channel race- 
ways, closure strips, and accessories shall be listed and 
identified for such use. 

II. Installation 

384.10 Uses Permitted. The use of strut-type channel 
raceways shall be permitted in the following: 

(1) Where exposed. 

(2) In dry locations. 

(3) In locations subject to corrosive vapors where pro- 
tected by finishes judged suitable for the condition. 

(4) Where the voltage is 600 volts or less. 

(5) As power poles. 

(6) In Class I, Division 2 hazardous (classified) locations 
as permitted in 501.4(B)(3). 

(7) As extensions of unbroken lengths through walls, par- 
titions, and floors where closure strips are removable 
from either side and the portion within the wall, parti- 
tion, or floor remains covered. 

(8) Ferrous channel raceways and fittings protected from 
corrosion solely by enamel shall be permitted only 
indoors. 

384.12 Uses Not Permitted. Strut type channel raceways 
shall not be used as follows: 

(1) Where concealed. 

(2) Ferrous channel raceways and fittings protected from 
corrosion solely by enamel shall not be permitted 
where subject to severe corrosive influences. 

384.21 Size of Conductors. No conductor larger than that 
for which the raceway is listed shall be installed in strut- 
type channel raceways. 

384.22 Number of Conductors. The number of conduc- 
tors permitted in strut-type channel raceways shall not ex- 





Area 


40% 


Area* 


25% 


Area 
















size 














Channel 


in. 2 


mm 2 


in. 2 


mm 2 


in. 2 


mm 2 


m x i3 /i6 


0.887 


572 


0.355 


229 


0.222 


143 


l 5 / 8 X 1 


1.151 


743 


0.460 


297 


0.288 


186 


l 5 /8 X P/ 8 


1.677 


1076 


0.671 


433 


0.419 


270 


l 5 /8 X l 5 /8 


2.028 


1308 


0.811 


523 


0.507 


327 


1% X 2 7 /l6 


3.169 


2045 


1.267 


817 


0.792 


511 


l 5 /8 X 3 l /4 


4.308 


2780 


1.723 


1112 


1.077 


695 


Vh x 3 / 4 


0.849 


548 


0.340 


219 


0.212 


137 


l'/ 2 x Vh 


1.828 


1179 


0.731 


472 


0.457 


295 


V/2X P/8 


2.301 


1485 


0.920 


594 


0.575 


371 


VAx 3 


3.854 


2487 


1.542 


995 


0.964 


622 



*Raceways with external joiners shall use a 40 percent wire fill cal- 
culation to determine the number of conductors permitted. 

Raceways with internal joiners shall use a 25 percent wire fill cal- 
culation to determine the number of conductors permitted. 



ceed the percentage fill using Table 384.22 and applicable 
outside diameter (O.D.) dimensions of specific types and 
sizes of wire given in the tables in Chapter 9. 

The derating factors of 310.15(B)(2)(a) shall not apply 
to conductors installed in strut-type channel raceways 
where all of the following conditions are met: 

(1) The cross-sectional area of the raceway exceeds 
2500 mm 2 (4 in. 2 ). 

(2) The current-carrying conductors do not exceed 30 in 
number. 

(3) The sum of the cross-sectional areas of all contained 
conductors does not exceed 20 percent of the interior 
cross-sectional area of the strut-type channel raceways. 
Formula for wire fill: 

ca 

n — — 
wa 

where: 
n = number of wires 
ca = channel area in square inches 
wa = wire area 

384.30 Securing and Supporting. 

(A) Surface Mount. A surface mount strut-type channel 
raceway shall be secured to the mounting surface with re- 
tention straps external to the channel at intervals not ex- 
ceeding 3 m (10 ft) and within 900 mm (3 ft) of each outlet 
box, cabinet, junction box, or other channel raceway termi- 
nation. 

(B) Suspension Mount. Strut-type channel raceways shall 
be permitted to be suspension mounted in air with approved 
appropriate methods designed for the purpose at intervals 



NATIONAL ELECTRICAL CODE 



2002 Edition 



70-216 



ARTICLE 386 — SURFACE METAL RACEWAYS 



not to exceed 3 m (10 ft) and within 900 mm (3 ft) of 
channel raceway terminations and ends. 

384.56 Splices and Taps. Splices and taps shall be permit- 
ted in raceways that are accessible after installation by hav- 
ing a removable cover. The conductors, including splices 
and taps, shall not fill the raceway to more than 75 percent 
of its area at that point. All splices and taps shall be made 
by approved methods. 

384.60 Grounding. Strut-type channel raceway enclosures 
providing a transition to or from other wiring methods shall 
have a means for connecting an equipment grounding con- 
ductor. Strut-type channel raceways shall be permitted as 
an equipment grounding conductor in accordance with 
250.118(14). Where a snap-fit metal cover for strut-type 
channel raceways is used to achieve electrical continuity in 
accordance with the listing, this cover shall not be permit- 
ted as the means for providing electrical continuity for a 
receptacle mounted in the cover. 

III. Construction Specifications 

384.100 Construction. Strut-type channel raceways and 
their accessories shall be of a construction that distin- 
guishes them from other raceways. Raceways and their el- 
bows, couplings, and other fittings shall be designed so that 
the sections can be electrically and mechanically coupled 
together and installed without subjecting the wires to abra- 
sion. They shall comply with 384.100(A), (B), and (C). 

(A) Material. Raceways and accessories shall be formed 
of steel, stainless steel, or aluminum. 

(B) Corrosion Protection. Steel raceways and accessories 
shall be protected against corrosion by galvanizing or an 
organic coating. 

FPN: Enamel and PVC coatings are examples of organic 
coatings that provide corrosion protection. 

(C) Cover. Covers of strut-type channel raceway shall be 
either metallic or nonmetallic. 

384.120 Marking. Each length of strut-type channel race- 
ways shall be clearly and durably identified as required in 
the first sentence of 110.21. 



ARTICLE 386 
Surface Metal Raceways 



I. General 

386.1 Scope. This article covers the use, installation, and 
construction specifications for surface metal raceways and 
associated fittings. 



386.2 Definition. 

Surface Metal Raceway. A metallic raceway that is in- 
tended to be mounted to the surface of a structure, with 
associated couplings, connectors, boxes, and fittings for the 
installation of electrical conductors. 

386.6 Listing Requirements. Surface metal raceway and 
associated fittings shall be listed. 

II. Installation 

386.10 Uses Permitted. The use of surface metal race- 
ways shall be permitted in the following: 

(1) In dry locations. 

(2) In Class I, Division 2 hazardous (classified) locations 
as permitted in 501.4(B)(3). 

(3) Under raised floors, as permitted in 645.5(D)(2). 

(4) Extension through walls and floors. Surface metal race- 
way shall be permitted to pass transversely through dry 
walls, dry partitions, and dry floors if the length pass- 
ing through is unbroken. Access to the conductors shall 
be maintained on both sides of the wall, partition, or 
floor. 

386.12 Uses Not Permitted. Surface metal raceways shall 
not be used in the following: 

(1) Where subject to severe physical damage, unless oth- 
erwise approved 

(2) Where the voltage is 300 volts or more between con- 
ductors, unless the metal has a thickness of not less 
than 1.02 mm (0.040 in.) nominal 

(3) Where subject to corrosive vapors 

(4) In hoistways 

(5) Where concealed, except as permitted in 386.10(4) 

386.21 Size of Conductors. No conductor larger than that 
for which the raceway is designed shall be installed in 
surface metal raceway. 

386.22 Number of Conductors or Cables. The number of 
conductors or cables installed in surface metal raceway 
shall not be greater than the number for which the raceway 
is designed. Cables shall be permitted to be installed where 
such use is permitted by the respective cable articles. 

The derating factors of 310.15(B)(2)(a) shall not apply 
to conductors installed in surface metal raceways where all 
of the following conditions are met: 

(1) The cross-sectional area of the raceway exceeds 
2500 mm 2 (4 in. 2 ) 

(2) The current-carrying conductors do not exceed 30 in 
number 



2002 Edition 



NATIONAL ELECTRICAL CODE 



ARTICLE 388 — SURFACE NONMETALLIC RACEWAYS 



70-217 



(3) The sum of the cross-sectional areas of all contained 
conductors does not exceed 20 percent of the interior 
cross-sectional area of the surface metal raceway 

386.56 Splices and Taps. Splices and taps shall be permit- 
ted in surface metal raceways having a removable cover 
that is accessible after installation. The conductors, includ- 
ing splices and taps, shall not fill the raceway to more than 
75 percent of its area at that point. Splices and taps in 
surface metal raceways without removable covers shall be 
made only in junction boxes. All splices and taps shall be 
made by approved methods. 

Taps of Type FC cable installed in surface metal race- 
way shall be made in accordance with 322.56(B). 

386.60 Grounding. Surface metal raceway enclosures pro- 
viding a transition from other wiring methods shall have a 
means for connecting an equipment grounding conductor. 

386.70 Combination Raceways. When combination sur- 
face metal raceways are used both for signaling and for 
lighting and power circuits, the different systems shall be 
run in separate compartments identified by sharply con- 
trasting colors of the interior finish, and the same relative 
position of compartments shall be maintained throughout 
the premises. 

III. Construction Specifications 

386.100 Construction. Surface metal raceways shall be of 
such construction as will distinguish them from other race- 
ways. Surface metal raceways and their elbows, couplings, 
and similar fittings shall be designed so that the sections 
can be electrically and mechanically coupled together and 
installed without subjecting the wires to abrasion. 

Where covers and accessories of nonmetallic materials 
are used on surface metal raceways, they shall be identified 
for such use. 



•Surface? Ndttmetallic Raceways 



I. General 

388.1 Scope. This article covers the use, installation, and 
construction specifications for surface nonmetallic race- 
ways and associated fittings. 

388.2 Definition. 

Surface Nonmetallic Raceway. A nonmetallic raceway 
that is intended to be mounted to the surface of a structure, 



with associated couplings, connectors, boxes, and fittings 
for the installation of electrical conductors. 

388.6 Listing Requirements. Surface nonmetallic race- 
way and associated fittings shall be listed. 

II. Installation 

388.10 Uses Permitted. Surface nonmetallic raceway shall 
be permitted as follows: 

(1) The use of surface nonmetallic raceways shall be per- 
mitted in dry locations. 

(2) Extension through walls and floors shall be permitted. 
Surface nonmetallic raceway shall be permitted to pass 
transversely through dry walls, dry partitions, and dry 
floors if the length passing through is unbroken. Access 
to the conductors shall be maintained on both sides of 
the wall, partition, or floor. 

388.12 Uses Not Permitted. Surface nonmetallic race- 
ways shall not be used in the following: 

(1) Where concealed, except as permitted in 388.10(2) 

(2) Where subject to severe physical damage 

(3) Where the voltage is 300 volts or more between con- 
ductors, unless listed for higher voltage 

(4) In hoistways 

(5) In any hazardous (classified) location except Class I, 
Division 2 locations as permitted in 501.4(B)(3) 

(6) Where subject to ambient temperatures exceeding those 
for which the nonmetallic raceway is listed 

(7) For conductors whose insulation temperature limita- 
tions would exceed those for which the nonmetallic 
raceway is listed 

388.21 Size of Conductors. No conductor larger than that 
for which the raceway is designed shall be installed in 
surface nonmetallic raceway. 

388.22 Number of Conductors or Cables. The number of 
conductors or cables installed in surface nonmetallic race- 
way shall not be greater than the number for which the 
raceway is designed. Cables shall be permitted to be in- 
stalled where such use is permitted by the respective cable 
articles. 

388.56 Splices and Taps. Splices and taps shall be permit- 
ted in surface nonmetallic raceways having a removable 
cover that is accessible after installation. The conductors, 
including splices and taps, shall not fill the raceway to more 
than 75 percent of its area at that point. Splices and taps in 
surface nonmetallic raceways without removable covers 
shall be made only in junction boxes. All splices and taps 
shall be made by approved methods. 



NATIONAL ELECTRICAL CODE 



2002 Edition 



70-218 



ARTICLE 390 — UNDERFLOOR RACEWAYS 



388.60 Grounding. Where equipment grounding is re- 
quired by Article 250, a separate equipment grounding con- 
ductor shall be installed in the raceway. 

388.70 Combination Raceways. When combination sur- 
face nonmetallic raceways are used both for signaling and 
for lighting and power circuits, the different systems shall 
be run in separate compartments identified by sharply con- 
trasting colors of the interior finish. 

III. Construction Specifications 

388.100 Construction. Surface nonmetallic raceways shall 
be of such construction as will distinguish them from other 
raceways. Surface nonmetallic raceways and their elbows, 
couplings, and similar fittings shall be designed so that the 
sections can be mechanically coupled together and installed 
without subjecting the wires to abrasion. 

Surface nonmetallic raceways and fittings are made of 
suitable nonmetallic material that is resistant to moisture 
and chemical atmospheres. It shall also be flame retardant, 
resistant to impact and crushing, resistant to distortion from 
heat under conditions likely to be encountered in service, 
and resistant to low-temperature effects. 

388.120 Marking. Surface nonmetallic raceways that have 
limited smoke-producing characteristics shall be permitted 
to be so identified. 



Underflpbr Raceways 



390.1 Scope. This article covers the use and installation 
requirements for underfloor raceways. 

390.2 Use. 

(A) Permitted. The installation of underfloor raceways 
shall be permitted beneath the surface of concrete or other 
flooring material or in office occupancies where laid flush 
with the concrete floor and covered with linoleum or 
equivalent floor covering. 

(B) Not Permitted. Underfloor raceways shall not be in- 
stalled (1) where subject to corrosive vapors or (2) in any 
hazardous (classified) locations, except as permitted by 
504.20 and in Class I, Division 2 locations as permitted in 
501.4(B)(3). Unless made of a material judged suitable for 
the condition or unless corrosion protection approved for 
the condition is provided, ferrous or nonferrous metal un- 
derfloor raceways, junction boxes, and fittings shall not be 



installed in concrete or in areas subject to severe corrosive 
influences. 

390.3 Covering. Raceway coverings shall comply with 
390.3(A) through (D). 

(A) Raceways Not Over 100 mm (4 in.) Wide. Half- 
round and flat-top raceways not over 100 mm (4 in.) in 
width shall have not less than 20 mm ( 3 A in.) of concrete or 
wood above the raceway. 

Exception: As permitted in 390.3(C) and (D) for flat-top 
raceways. 

(B) Raceways Over 100 mm (4 in.) Wide But Not Over 
200 mm (8 in.) Wide. Flat-top raceways over 100 mm (4 in.) 
but not over 200 mm (8 in.) wide with a minimum of 25 mm 
(1 in.) spacing between raceways shall be covered with con- 
crete to a depth of not less than 25 mm (1 in.). Raceways 
spaced less than 25 mm (1 in.) apart shall be covered with 
concrete to a depth of 38 mm (IV2 in.). 

(C) Trench-Type Raceways Flush with Concrete. Trench- 
type flush raceways with removable covers shall be permit- 
ted to be laid flush with the floor surface. Such approved 
raceways shall be designed so that the cover plates provide 
adequate mechanical protection and rigidity equivalent to 
junction box covers. 

(D) Other Raceways Flush with Concrete. In office oc- 
cupancies, approved metal flat-top raceways, if not over 
100 mm (4 in.) in width, shall be permitted to be laid flush 
with the concrete floor surface, provided they are covered 
with substantial linoleum that is not less than 1.6 mm (V\6 
in.) thick or with equivalent floor covering. Where more 
than one and not more than three single raceways are each 
installed flush with the concrete, they shall be contiguous 
with each other and joined to form a rigid assembly. 

390.4 Size of Conductors. No conductor larger than that 
for which the raceway is designed shall be installed in 
underfloor raceways. 

390.5 Maximum Number of Conductors in Raceway. 

The combined cross-sectional area of all conductors or 
cables shall not exceed 40 percent of the interior cross- 
sectional area of the raceway. 

390.6 Splices and Taps. Splices and taps shall be made 
only in junction boxes. 

For the purposes of this section, so-called loop wiring 
(continuous, unbroken conductor connecting the individual 
outlets) shall not be considered to be a splice or tap. 

Exception: Splices and taps shall be permitted in trench- 
type flush raceway having a removable cover that is acces- 



2002 Edition 



NATIONAL ELECTRICAL CODE 



ARTICLE 392 — CABLE TRAYS 



70-219 



sible after installation. The conductors, including splices 
and taps, shall not fill more than 75 percent of the raceway 
area at that point. 



ARTICLE 392 
Cable Trays 



390.7 Discontinued Outlets. When an outlet is aban- 
doned, discontinued, or removed, the sections of circuit 
conductors supplying the outlet shall be removed from the 
raceway. No splices or reinsulated conductors, such as 
would be the case with abandoned outlets on loop wiring, 
shall be allowed in raceways. 

390.8 Laid in Straight Lines. Underfloor raceways shall 
be laid so that a straight line from the center of one junction 
box to the center of the next junction box coincides with 
the centerline of the raceway system. Raceways shall be 
firmly held in place to prevent disturbing this alignment 
during construction. 

390.9 Markers at Ends. A suitable marker shall be in- 
stalled at or near each end of each straight run of raceways 
to locate the last insert. 

390.10 Dead Ends. Dead ends of raceways shall be 
closed. 

390.13 Junction Boxes. Junction boxes shall be leveled to 
the floor grade and sealed to prevent the free entrance of 
water or concrete. Junction boxes used with metal raceways 
shall be metal and shall be electrically continuous with the 
raceways. 

390.14 Inserts. Inserts shall be leveled and sealed to pre- 
vent the entrance of concrete. Inserts used with metal race- 
ways shall be metal and shall be electrically continuous 
with the raceway. Inserts set in or on fiber raceways before 
the floor is laid shall be mechanically secured to the race- 
way. Inserts set in fiber raceways after the floor is laid shall 
be screwed into the raceway. When cutting through the 
raceway wall and setting inserts, chips and other dirt shall 
not be allowed to remain in the raceway, and tools shall be 
used that are designed so as to prevent the tool from enter- 
ing the raceway and damaging conductors that may be in 
place. 

390.15 Connections to Cabinets and Wall Outlets. Con- 
nections from underfloor raceways to distribution centers 
and wall outlets shall be made by approved fittings or by 
any of the wiring methods in Chapter 3, where installed in 
accordance with the provisions of the respective articles. 



392.1 Scope. This article covers cable tray systems, in- 
cluding ladder, ventilated trough, ventilated channel, solid 
bottom, and other similar structures. 

FPN: For further information on cable trays, see 
NEMA-VE 1, 1998-Meta/ Cable Tray Systems; 
NEMA-VE 2-1996, Metal Cable Tray Installation Guide- 
lines; and NEMA-FG-, 1998, Nonmetallic Cable Tray 
Systems. 

392.2 Definition. 

Cable Tray System. A unit or assembly of units or sections 
and associated fittings forming a structural system used to 
securely fasten or support cables and raceways. 

392.3 Uses Permitted. Cable tray shall be permitted to be 
used as a support system for services, feeders, branch cir- 
cuits, communications circuits, control circuits, and signal- 
ing circuits. Cable tray installations shall not be limited to 
industrial establishments. Where exposed to direct rays of 
the sun, insulated conductors and jacketed cables shall be 
identified as being sunlight resistant. Cable trays and their 
associated fittings shall be identified for the intended use. 

(A) Wiring Methods. The wiring methods in Table 
392.3(A) shall be permitted to be installed in cable tray 
systems under the conditions described in their respective 
articles and sections. 

(B) In Industrial Establishments. The wiring methods in 
Table 392.3(A) shall be permitted to be used in any indus- 
trial establishment under the conditions described in their 
respective articles. In industrial establishments only, where 
conditions of maintenance and supervision ensure that only 
qualified persons service the installed cable tray system, 
any of the cables in 392.3(B)(1) and (2) shall be permitted 
to be installed in ladder, ventilated trough, solid bottom, or 
ventilated channel cable trays. 

(1) Single Conductors. Single-conductor cables shall be 
permitted to be installed in accordance with the following: 

(a) Single-conductor cable shall be 1/0 AWG or larger 
and shall be of a type listed and marked on the surface for 
use in cable trays. Where 1/0 AWG through 4/0 AWG 
single-conductor cables are installed in ladder cable tray, 
the maximum allowable rung spacing for the ladder cable 
tray shall be 230 mm (9 in.). 

(b) Welding cables shall comply with the provisions of 
Article 630, Part IV. 



NATIONAL ELECTRICAL CODE 



2002 Edition 



70-220 



ARTICLE 392 — CABLE TRAYS 



Table 392.3(A) Wiring Methods 



Wiring Method 


Article Section 


Armored cable 


320 


Communication raceways 


800 


Electrical metallic tubing 


358 


Electrical nonmetallic tubing 


362 


Fire alarm cables 


760 


Flexible metal conduit 


348 


Flexible metallic tubing 


360 


Instrumentation tray cable 


727 


Intermediate metal conduit 


342 


Liquidtight flexible metal 


350 


conduit 




Liquidtight flexible nonmetallic 


356 


conduit 




Metal-clad cable 


330 


Mineral-insulated, 


332 


metal-sheathed cable 




Multiconductor service-entrance 


338 


cable 




Multiconductor underground 


340 


feeder and branch-circuit cable 




Multipurpose and 


800 


communications cables 




Nonmetallic-sheathed cable 


334 


Power and control tray cable 


336 


Power-limited tray cable 


725.61(C) and 




725.71(F) 


Optical fiber cables 


770 


Optical fiber raceways 


770 


Other factory-assembled, 




multiconductor control, signal, 




or power cables that are 




specifically approved for 




installation in cable trays 




Rigid metal conduit 


344 


Rigid nonmetallic conduit 


352 



(c) Single conductors used as equipment grounding 
conductors shall be insulated, covered, or bare, and they 
shall be 4 AWG or larger. 

(2) Medium Voltage. Single- and multiconductor medium 
voltage cables shall be Type MV cable (Article 328). Single 
conductors shall be installed in accordance with 
392.3(B)(1). 

(C) Equipment Grounding Conductors. Metallic cable 
trays shall be permitted to be used as equipment grounding 
conductors where continuous maintenance and supervision 
ensure that qualified persons service the installed cable tray 
system and the cable tray complies with provisions of 
392.7. 

(D) Hazardous (Classified) Locations. Cable trays in 
hazardous (classified) locations shall contain only the cable 
types permitted in 501.4, 502.4, 503.3, 504.20, and 505.15. 

(E) Nonmetallic Cable Tray. In addition to the uses per- 
mitted elsewhere in Article 392, nonmetallic cable tray 



shall be permitted in corrosive areas and in areas requiring 
voltage isolation. 

392.4 Uses Not Permitted. Cable tray systems shall not be 
used in hoist ways or where subject to severe physical dam- 
age. Cable tray systems shall not be used in environmental 
airspaces, except as permitted in 300.22, to support wiring 
methods recognized for use in such spaces. 

392.5 Construction Specifications. 

(A) Strength and Rigidity. Cable trays shall have suitable 
strength and rigidity to provide adequate support for all 
contained wiring. 

(B) Smooth Edges. Cable trays shall not have sharp edges, 
burrs, or projections that could damage the insulation or 
jackets of the wiring. 

(C) Corrosion Protection. Cable tray systems shall be 
corrosion resistant. If made of ferrous material, the system 
shall be protected from corrosion as required by 300.6. 

(D) Side Rails. Cable trays shall have side rails or equiva- 
lent structural members. 

(E) Fittings. Cable trays shall include fittings or other suit- 
able means for changes in direction and elevation of runs. 

(F) Nonmetallic Cable Tray. Nonmetallic cable trays 
shall be made of flame-retardant material. 

392.6 Installation. 

(A) Complete System. Cable trays shall be installed as a 
complete system. Field bends or modifications shall be 
made so that the electrical continuity of the cable tray sys- 
tem and support for the cables is maintained. Cable tray 
systems shall be permitted to have mechanically discon- 
tinuous segments between cable tray runs or between cable 
tray runs and equipment. The system shall provide for the 
support of the cables in accordance with their correspond- 
ing articles. 

Where cable trays support individual conductors and 
where the conductors pass from one cable tray to another, 
or from a cable tray to raceway(s) or from a cable tray to 
equipment where the conductors are terminated, the dis- 
tance between cable trays or between the cable tray and the 
raceway(s) or the equipment shall not exceed 1.8 m (6 ft). 
The conductors shall be secured to the cable tray(s) at the 
transition, and they shall be protected, by guarding or by 
location, from physical damage. 

A bonding jumper sized in accordance with 250.102 
shall connect the two sections of cable tray, or the cable 
tray and the raceway or equipment. Bonding shall be in 
accordance with 250.96. 



2002 Edition 



NATIONAL ELECTRICAL CODE 



ARTICLE 392 — CABLE TRAYS 



70-221 



(B) Completed Before Installation. Each run of cable 
tray shall be completed before the installation of cables. 

(C) Supports. Supports shall be provided to prevent stress 
on cables where they enter raceways or other enclosures 
from cable tray systems. 

Cable trays shall be supported at intervals in accordance 
with the installation instructions. 

(D) Covers. In portions of runs where additional protec- 
tion is required, covers or enclosures providing the required 
protection shall be of a material that is compatible with the 
cable tray. 

(E) Multiconductor Cables Rated 600 Volts or Less. 

Multiconductor cables rated 600 volts or less shall be per- 
mitted to be installed in the same cable tray. 

(F) Cables Rated Over 600 Volts. Cables rated over 600 
volts and those rated 600 volts or less installed in the same 
cable tray shall comply with either of the following: 

(1) The cables rated over 600 volts are Type MC. 

(2) The cables rated over 600 volts are separated from the 
cables rated 600 volts or less by a solid fixed barrier of 
a material compatible with the cable tray. 

(G) Through Partitions and Walls. Cable trays shall be 
permitted to extend transversely through partitions and 
walls or vertically through platforms and floors in wet or 
dry locations where the installations, complete with in- 
stalled cables, are made in accordance with the require- 
ments of 300.21. 

(H) Exposed and Accessible. Cable trays shall be exposed 
and accessible except as permitted by 392.6(G). 

(I) Adequate Access. Sufficient space shall be provided 
and maintained about cable trays to permit adequate access 
for installing and maintaining the cables. 

(J) Raceways, Cables, Boxes, and Conduit Bodies Sup- 
ported from Cable Tray Systems. In industrial facilities 
where conditions of maintenance and supervision ensure 
that only qualified persons service the installation and 
where the cable tray systems are designed and installed to 
support the load, such systems shall be permitted to support 
raceways and cables, and boxes and conduit bodies covered 
in 314.1. For raceways terminating at the tray, a listed cable- 
tray clamp or adapter shall be used to securely fasten the 
raceway to the cable tray system. Additional supporting and 
securing of the raceway shall be in accordance with the 
requirements of the appropriate raceway article. 

For raceways or cables running parallel to and attached 
to the bottom or side of a cable tray system, fastening and 
supporting shall be in accordance with the requirements of 
the appropriate raceway or cable article. 



For boxes and conduit bodies attached to the bottom or 
side of a cable tray system, fastening and supporting shall 
be in accordance with the requirements of 314.23. 

392.7 Grounding. 

(A) Metallic Cable Trays. Metallic cable trays that sup- 
port electrical conductors shall be grounded as required for 
conductor enclosures in Article 250. 

(B) Steel or Aluminum Cable Tray Systems. Steel or 
aluminum cable tray systems shall be permitted to be used 
as equipment grounding conductors, provided that all the 
following requirements are met: 

(1) The cable tray sections and fittings shall be identified 
for grounding purposes. 

(2) The minimum cross-sectional area of cable trays shall 
conform to the requirements in Table 392.7(B). 

(3) All cable tray sections and fittings shall be legibly and 
durably marked to show the cross-sectional area of 
metal in channel cable trays, or cable trays of one-piece 
construction, and the total cross-sectional area of both 
side rails for ladder or trough cable trays. 

(4) Cable tray sections, fittings, and connected raceways 
shall be bonded in accordance with 250.96 using bolted 
mechanical connectors or bonding jumpers sized and 
installed in accordance with 250.102. 

392.8 Cable Installation. 

(A) Cable Splices. Cable splices made and insulated by 
approved methods shall be permitted to be located within a 
cable tray, provided they are accessible and do not project 
above the side rails. 

(B) Fastened Securely. In other than horizontal runs, the 
cables shall be fastened securely to transverse members of 
the cable trays. 

(C) Bushed Conduit and Tubing. A box shall not be re- 
quired where cables or conductors are installed in bushed 
conduit and tubing used for support or for protection 
against physical damage. 

(D) Connected in Parallel. Where single conductor cables 
comprising each phase or neutral of a circuit are connected 
in parallel as permitted in 310.4, the conductors shall be 
installed in groups consisting of not more than one conduc- 
tor per phase or neutral to prevent current unbalance in the 
paralleled conductors due to inductive reactance. 

Single conductors shall be securely bound in circuit 
groups to prevent excessive movement due to fault-current 
magnetic forces unless single conductors are cabled to- 
gether, such as triplexed assemblies. 

(E) Single Conductors. Where any of the single conduc- 
tors installed in ladder or ventilated trough cable trays are 



NATIONAL ELECTRICAL CODE 



2002 Edition 



70-222 



ARTICLE 392 — CABLE TRAYS 



Table 392.7(B) Metal Area Requirements for Cable Trays 
Used as Equipment Grounding Conductor 



Maximum Fuse 








Ampere Rating, 








Circuit Breaker 








Ampere Trip Setting, 








or Circuit Breaker 


Minimum Cross-Sectional 


Protective Relay 




Area of Metal 3 




Ampere Trip Setting 














for Ground-Fault 




Aluminum 


Protection of Any 


Steel Cable Trays Cable 


Trays 


Cable Circuit in the 








Cable Tray System 


mm 2 


in. 2 mm 2 


in. 2 


60 


129 


0.20 129 


0.20 


100 


258 


0.40 129 


0.20 


200 


451.5 


0.70 129 


0.20 


400 


645 


1.00 258 


0.40 


600 


967.5 


1.50 b 258 


0.40 


1000 


— 


— 387 


0.60 


1200 


— 


— 645 


1.00 


1600 


— 


— 967.5 


1.50 


2000 


— 


— 1290 


2.00 b 



a Total cross-sectional area of both side rails for ladder or trough cable 
trays; or the minimum cross-sectional area of metal in channel cable 
trays or cable trays of one-piece construction. 

b Steel cable trays shall not be used as equipment grounding conduc- 
tors for circuits with ground-fault protection above 600 amperes. Alu- 
minum cable trays shall not be used as equipment grounding conduc- 
tors for circuits with ground-fault protection above 2000 amperes. 



1/0 through 4/0 AWG, all single conductors shall be in- 
stalled in a single layer. Conductors that are bound together 
to comprise each circuit group shall be permitted to be 
installed in other than a single layer. 

392.9 Number of Multiconductor Cables, Rated 2000 
Volts or Less, in Cable Trays. The number of multicon- 
ductor cables, rated 2000 volts or less, permitted in a single 
cable tray shall not exceed the requirements of this section. 
The conductor sizes herein apply to both aluminum and 
copper conductors. 

(A) Any Mixture of Cables. Where ladder or ventilated 
trough cable trays contain multiconductor power or lighting 
cables, or any mixture of multiconductor power, lighting, 
control, and signal cables, the maximum number of cables 
shall conform to the following: 

(1) Where all of the cables are 4/0 AWG or larger, the sum 
of the diameters of all cables shall not exceed the cable 
tray width, and the cables shall be installed in a single 
layer. 

(2) Where all of the cables are smaller than 4/0 AWG, the 
sum of the cross-sectional areas of all cables shall not 
exceed the maximum allowable cable fill area in Col- 
umn 1 of Table 392.9 for the appropriate cable tray 
width. 



(3) Where 4/0 AWG or larger cables are installed in the 
same cable tray with cables smaller than 4/0 AWG, the 
sum of the cross-sectional areas of all cables smaller 
than 4/0 AWG shall not exceed the maximum allow- 
able fill area resulting from the computation in Column 
2 of Table 392.9 for the appropriate cable tray width. 
The 4/0 AWG and larger cables shall be installed in a 
single layer, and no other cables shall be placed on 
them. 

(B) Multiconductor Control and/or Signal Cables Only. 

Where a ladder or ventilated trough cable tray having a 
usable inside depth of 150 mm (6 in.) or less contains 
multiconductor control and/or signal cables only, the sum 
of the cross-sectional areas of all cables at any cross section 
shall not exceed 50 percent of the interior cross-sectional 
area of the cable tray. A depth of 150 mm (6 in.) shall be 
used to compute the allowable interior cross-sectional area 
of any cable tray that has a usable inside depth of more than 
150 mm (6 in.). 

(C) Solid Bottom Cable Trays Containing Any Mixture. 

Where solid bottom cable trays contain multiconductor 
power or lighting cables, or any mixture of multiconductor 
power, lighting, control, and signal cables, the maximum 
number of cables shall conform to the following: 

(1) Where all of the cables are 4/0 AWG or larger, the sum 
of the diameters of all cables shall not exceed 90 per- 
cent of the cable tray width, and the cables shall be 
installed in a single layer. 

(2) Where all of the cables are smaller than 4/0 AWG, the 
sum of the cross-sectional areas of all cables shall not 
exceed the maximum allowable cable fill area in Col- 
umn 3 of Table 392.9 for the appropriate cable tray 
width. 

(3) Where 4/0 AWG or larger cables are installed in the 
same cable tray with cables smaller than 4/0 AWG, the 
sum of the cross-sectional areas of all cables smaller 
than 4/0 AWG shall not exceed the maximum allow- 
able fill area resulting from the computation in Column 
4 of Table 392.9 for the appropriate cable tray width. 
The 4/0 AWG and larger cables shall be installed in a 
single layer, and no other cables shall be placed on 
them. 

(D) Solid Bottom Cable Tray — Multiconductor Con- 
trol andfor Signal Cables Only. Where a solid bottom 
cable tray having a usable inside depth of 150 mm (6 in.) or 
less contains multiconductor control and/or signal cables 
only, the sum of the cross-sectional areas of all cables at 
any cross section shall not exceed 40 percent of the interior 
cross-sectional area of the cable tray. A depth of 150 mm 
(6 in.) shall be used to compute the allowable interior 
cross-sectional area of any cable tray that has a usable 
inside depth of more than 150 mm (6 in.). 



• 



2002 Edition 



NATIONAL ELECTRICAL CODE 



ARTICLE 392 — CABLE TRAYS 



70-223 



Table 392.9 Allowable Cable Fill Area for Multiconductor Cables in Ladder, Ventilated Trough, or 
Solid Bottom Cable Trays for Cables Rated 2000 Volts or Less 





Maximum Allowable Fill Area for Multiconductor Cables 




Ladder or Ventilated Trough Cable Trays, 

392.9(A) 


Solid Bottom Cable Trays, 392.9(C) 


Inside Width of 
Cable Tray 


Column 1 

Applicable for 

392.9(A)(2) Only 


Column 2 a 

Applicable for 

392.9(A)(3) Only 


Column 3 

Applicable for 

392.9(C)(2) Only 


Column 4 a 

Applicable for 

392.9(C)(3) Only 


mm in. 


mm 2 in. 2 


mm 2 in. 2 


mm in. 


mm 2 in. 2 


150 6.0 
225 9.0 
300 12.0 
450 18.0 
600 24.0 
750 30.0 
900 36.0 


4,500 7.0 
6,800 10.5 
9,000 14.0 
13,500 21.0 
18,000 28.0 
22,500 35.0 
27,000 42.0 


4,500 - (1.2 Sd) b 7 - (1.2 Sd) b 
6,800 - (1.2 Sd) 10.5- (1.2 Sd) 
9,000 - (1.2 Sd) 14 - (1.2 Sd) 
13,500- (1.2 Sd) 21 - (1.2 Sd) 
18,000 - (1.2 Sd) 28 - (1.2 Sd) 
22,500 - (1.2 Sd) 35 - (1.2 Sd) 
27,000 - (1.2 Sd) 42 - (1.2 Sd) 


3,500 5.5 
5,100 8.0 
7,100 11.0 
10,600 16.5 
14,200 22.0 
17,700 27.5 
21,300 33.0 


3,500 - Sd b 5.5 - Sdb 
5,100 - Sd 8.0 - Sd 
7,100 -Sd 11.0 -Sd 
10,600 - Sd 16.5 - Sd 
14,200 - Sd 22.0 - Sd 
17,700 - Sd 27.5 - Sd 
21,300 - Sd 33.0 - Sd 



The maximum allowable fill areas in Columns 2 and 4 shall be computed. For example, the maximum allowable fill 

in mm 2 for a 150-mm wide cable tray in Column 2 shall be 4500 minus (1.2 multiplied by Sd) [the maximum allowable fill, 

in square inches, for a 6-in. wide cable tray in Column 2 shall be 7 minus (1.2 multiplied by Sd)]. 

The term Sd in Columns 2 and 4 is equal to the sum of the diameters, in mm, of all cables 107.2 mm 

(in inches, of all 4/0 AWG) and larger multiconductor cables in the same cable tray with smaller cables. 



(E) Ventilated Channel Cable Trays. Where ventilated 
channel cable trays contain multiconductor cables of any 
type, the following shall apply: 

(1) Where only one multiconductor cable is installed, the 
cross-sectional area shall not exceed the value specified 
in Column 1 of Table 392.9(E). 

(2) Where more than one multiconductor cable is installed, 
the sum of the cross-sectional area of all cables shall 
not exceed the value specified in Column 2 of Table 
392.9(E). 

(F) Solid Channel Cable Trays. Where solid channel 
cable trays contain multiconductor cables of any type, the 
following shall apply: 



Table 392.9(E) Allowable Cable Fill Area for Multiconductor 
Cables in Ventilated Channel Cable Trays for Cables Rated 
2000 Volts or Less 

Maximum Allowable Fill Area for 
Multiconductor Cables 



Inside Width of 
Cable Tray 



Column 1 
One Cable 

nm 2 in. 2 



Column 2 
More Than 
One Cable 

2 • 2 

nm in. 



75 


3 


1500 


2.3 


850 


1.3 


100 


4 


2900 


4.5 


1600 


2.5 


150 


6 


4500 


7.0 


2450 


3.8 



(1) Where only one multiconductor cable is installed, the 
cross-sectional area of the cable shall not exceed the 
value specified in Column 1 of Table 392.9(F). 

(2) Where more than one multiconductor cable is installed, 
the sum of the cross-sectional area of all cable shall not 
exceed the value specified in Column 2 of Table 
392.9(F). 

392.10 Number of Single-Conductor Cables, Rated 
2000 Volts or Less, in Cable Trays. The number of single- 
conductor cables, rated 2000 volts or less, permitted in a 
single cable tray section shall not exceed the requirements 
of this section. The single conductors, or conductor assem- 
blies, shall be evenly distributed across the cable tray. The 
conductor sizes herein apply to both aluminum and copper 
conductors. 



Table 392.9(F) Allowable Cable Fill Area for Multiconductor 
Cables in Solid Channel Cable Trays for Cables Rated 2000 
Volts or Less 



NATIONAL ELECTRICAL CODE 











Column 2 


Inside Width of 


Column 1 


More Than 


Cable 


Tray 


One Cable 


One Cable 


mm 


in. 


mm 2 


in. 2 


mm 2 


in. 2 


50 


2 


850 


1.3 


500 


0.8 


75 


3 


1300 


2.0 


700 


1.1 


100 


4 


2400 


3.7 


1400 


2.1 


150 


6 


3600 


5.5 


2100 


3.2 










2002 Edition 



70-224 



ARTICLE 392 — CABLE TRAYS 



(A) Ladder or Ventilated Trough Cable Trays. Where 
ladder or ventilated trough cable trays contain single- 
conductor cables, the maximum number of single conduc- 
tors shall conform to the following: 

(1) Where all of the cables are 1000 kcmil or larger, the 
sum of the diameters of all single-conductor cables 
shall not exceed the cable tray width. 

(2) Where all of the cables are from 250 kcmil up to 1000 
kcmil, the sum of the cross-sectional areas of all single- 
conductor cables shall not exceed the maximum allow- 
able cable fill area in Column 1 of Table 392.10(A) for 
the appropriate cable tray width. 

(3) Where 1000 kcmil or larger single-conductor cables are 
installed in the same cable tray with single-conductor 
cables smaller than 1000 kcmil, the sum of the cross- 
sectional areas of all cables smaller than 1000 kcmil 
shall not exceed the maximum allowable fill area re- 
sulting from the computation in Column 2 of Table 
392.10(A) for the appropriate cable tray width. 

(4) Where any of the single conductor cables are 1/0 
through 4/0 AWG, the sum of the diameters of all 
single conductor cables shall not exceed the cable tray 
width. 

(B) Ventilated Channel Cable Trays. Where 50 mm 
(2 in.), 75 mm (3 in.), 100 mm (4 in.), or 150 mm (6 in.) 
wide ventilated channel cable trays contain single- 
conductor cables, the sum of the diameters of all single 
conductors shall not exceed the inside width of the channel. 

392.11 Ampacity of Cables, Rated 2000 Volts or Less, in 
Cable Trays. 

(A) Multiconductor Cables. The allowable ampacity of 
multiconductor cables, nominally rated 2000 volts or less, 



installed according to the requirements of 392.9 shall be as 
given in Tables 310.16 and 310.18, subject to the provi- 
sions of (1), (2), (3), and 310.15(A)(2). 

(1) The derating factors of 310.15(B)(2)(a) shall apply 
only to multiconductor cables with more than three 
current-carrying conductors. Derating shall be limited 
to the number of current-carrying conductors in the 
cable and not to the number of conductors in the cable 
tray. 

(2) Where cable trays are continuously covered for more 
than 1.8 m (6 ft) with solid un ventilated covers, not 
over 95 percent of the allowable ampacities of Tables 
310.16 and 310.18 shall be permitted for multiconduc- 
tor cables. 

(3) Where multiconductor cables are installed in a single 
layer in uncovered trays, with a maintained spacing of 
not less than one cable diameter between cables, the 
ampacity shall not exceed the allowable ambient 
temperature-corrected ampacities of multiconductor 
cables, with not more than three insulated conductors 
rated through 2000 volts in free air, in accordance 
with 310.15(C). 

FPN: See Table B.310.3. 

(B) Single-Conductor Cables. The allowable ampacity of 
single-conductor cables shall be as permitted by 
310.15(A)(2). The derating factors of 310.15(B)(2)(a) shall 
not apply to the ampacity of cables in cable trays. The 
ampacity of single-conductor cables, or single conductors 
cabled together (triplexed, quadruplexed, etc.), nominally 
rated 2000 volts or less shall comply with the following: 

(1) Where installed according to the requirements of 
392.10, the ampacities for 600 kcmil and larger single- 



Table 392.10(A) Allowable Cable Fill Area for Single-Conductor Cables in Ladder 
or Ventilated Trough Cable Trays for Cables Rated 2000 Volts or Less 





Maximum Allowable Fill Area i 


or Single-Conductor Cables 


in Ladder or 






Ventilated 


Trough Cable Trays 






Column 1 




Column 2 a 


Inside Width of Cable Tray 


Applicable for 392.10(A)(2) Only 
mm 2 in. 2 


Applicable for 392.10(A)(3) Only 


mm in. 


mm 2 


in. 2 


150 6 


4,200 


6.5 


4,200-(l.lSd) b 


6.5-(l.lSd) b 


225 9 


6,100 


9.5 


6,100-(1.1 Sd) 


9.5-(l.l Sd) 


300 12 


8,400 


13.0 


8,400-(l.l Sd) 


13.0-Q.l Sd) 


450 18 


12,600 


19.5 


12,600-(1.1 Sd) 


19.5— (1.1 Sd) 


600 24 


16,800 


26.0 


16,800-(1.1 Sd) 


26.0-(l.l Sd) 


750 30 


21,000 


32.5 


21,000-(1.1 Sd) 


32.5-(l.l Sd) 


900 36 


25,200 


39.0 


25,200-(l.l Sd) 


39.0-(l.l Sd) 



'The maximum allowable fill areas in Column 2 shall be computed. For example, the maximum allowable fill, in 

mm 2 for a 150 mm wide cable tray in Column 2 shall be 4192.5 minus (1.1 multiplied by Sd) [the maximum allowable fill, 

in square inches, for a 6-in. wide cable tray in Column 2 shall be 6.5 minus (1.1 multiplied by Sd)]. 

b The term Sd in Column 2 is equal to the sum of the diameters, in mm, of all cables 507 mm 2 

(in inches, of all 1000 kcmil) and larger single-conductor cables in the same ladder or ventilated trough cable tray with small cables. 



2002 Edition 



NATIONAL ELECTRICAL CODE 



ARTICLE 394 — CONCEALED KNOB-AND-TUBE WIRING 



70-225 



conductor cables in uncovered cable trays shall not ex- 
ceed 75 percent of the allowable ampacities in Tables 
310.17 and 310.19. Where cable trays are continuously 
covered for more than 1.8 m (6 ft) with solid unventi- 
lated covers, the ampacities for 600 kcmil and larger 
cables shall not exceed 70 percent of the allowable 
ampacities in Tables 310.17 and 310.19. 

(2) Where installed according to the requirements of 
392.10, the ampacities for 1/0 AWG through 500 kcmil 
single-conductor cables in uncovered cable trays shall 
not exceed 65 percent of the allowable ampacities in 
Tables 310.17 and 310.19. Where cable trays are con- 
tinuously covered for more than 1.8 m (6 ft) with solid 
un ventilated covers, the ampacities for 1/0 AWG 
through 500 kcmil cables shall not exceed 60 percent 
of the allowable ampacities in Tables 310.17 and 
310.19. 

(3) Where single conductors are installed in a single layer 
in uncovered cable trays, with a maintained space of 
not less than one cable diameter between individual 
conductors, the ampacity of 1/0 AWG and larger cables 
shall not exceed the allowable ampacities in Tables 
310.17 and 310.19. 

(4) Where single conductors are installed in a triangular or 
square configuration in uncovered cable trays, with a 
maintained free airspace of not less than 2.15 times one 
conductor diameter (2.15 x O.D.) of the largest con- 
ductor contained within the configuration and adjacent 
conductor configurations or cables, the ampacity of 1/0 
AWG and larger cables shall not exceed the allowable 
ampacities of two or three single insulated conductors 
rated through 2000 volts supported on a messenger in 
accordance with 310.15(B). 

FPN: See Table 310.20. 

392.12 Number of Type MV and Type MC Cables (2001 
Volts or Over) in Cable Trays. The number of cables rated 
2001 volts or over permitted in a single cable tray shall not 
exceed the requirements of this section. 

The sum of the diameters of single-conductor and mul- 
ticonductor cables shall not exceed the cable tray width, 
and the cables shall be installed in a single layer. Where 
single conductor cables are triplexed, quadruplexed, or 
bound together in circuit groups, the sum of the diameters 
of the single conductors shall not exceed the cable tray 
width, and these groups shall be installed in single layer 
arrangement. 

392.13 Ampacity of Type MV and Type MC Cables 
(2001 Volts or Over) in Cable Trays. The ampacity of 
cables, rated 2001 volts, nominal, or over, installed accord- 
ing to 392.12 shall not exceed the requirements of this 
section. 



(A) Multiconductor Cables (2001 Volts or Over). The 

allowable ampacity of multiconductor cables shall be as 
given in Tables 310.75 and 310.76, subject to the following 
provisions: 

(1) Where cable trays are continuously covered for more 
than 1.8 m (6 ft) with solid unventilated covers, not 
more than 95 percent of the allowable ampacities of 
Tables 310.75 and 310.76 shall be permitted for multi- 
conductor cables. 

(2) Where multiconductor cables are installed in a single 
layer in uncovered cable trays, with maintained spacing 
of not less than one cable diameter between cables, the 
ampacity shall not exceed the allowable ampacities of 
Tables 310.71 and 310.72. 

(B) Single-Conductor Cables (2001 Volts or Over). The 

ampacity of single-conductor cables, or single conductors 
cabled together (triplexed, quadruplexed, etc.), shall com- 
ply with the following: 

(1) The ampacities for 1/0 AWG and larger single- 
conductor cables in uncovered cable trays shall not ex- 
ceed 75 percent of the allowable ampacities in Tables 
310.69 and 310.70. Where the cable trays are covered 
for more than 1.8 m (6 ft) with solid unventilated cov- 
ers, the ampacities for 1/0 AWG and larger single- 
conductor cables shall not exceed 70 percent of the 
allowable ampacities in Tables 310.69 and 310.70. 

(2) Where single-conductor cables are installed in a single 
layer in uncovered cable trays, with a maintained space 
of not less than one cable diameter between individual 
conductors, the ampacity of 1/0 AWG and larger cables 
shall not exceed the allowable ampacities in Tables 
310.69 and 310.70. 

(3) Where single conductors are installed in a triangular or 
square configuration in uncovered cable trays, with a 
maintained free air space of not less than 2.15 times the 
diameter (2.15 x O.D.) of the largest conductor con- 
tained within the configuration and adjacent conductor 
configurations or cables, the ampacity of 1/0 AWG and 
larger cables shall not exceed the allowable ampacities 
in Tables 310.67 and 310.68. 



I. General 

394.1 Scope. This article covers the use, installation, and 
construction specifications of concealed knob-and-tube wiring. 



NATIONAL ELECTRICAL CODE 



2002 Edition 



70-226 



ARTICLE 394 — CONCEALED KNOB-AND-TUBE WIRING 



394.2. Definition. 

Concealed Knob-and-Tube Wiring. A wiring method us- 
ing knobs, tubes, and flexible nonmetallic tubing for the 
protection and support of single insulated conductors. 

II. Installation 

394.10 Uses Permitted. Concealed knob-and-tube wiring 
shall be permitted to be installed in the hollow spaces of 
walls and ceilings or in unfinished attics and roof spaces as 
provided in 394.23 only as follows: 

(1) For extensions of existing installations 

(2) Elsewhere by special permission 

394.12 Uses Not Permitted. Concealed knob-and-tube 
wiring shall not be used in the following: 

(1) Commercial garages 

(2) Theaters and similar locations 

(3) Motion picture studios 

(4) Hazardous (classified) locations 

(5) Hollow spaces of walls, ceilings, and attics where such 
spaces are insulated by loose, rolled, or foamed-in- 
place insulating material that envelops the conductors 

394.17 Through or Parallel to Framing Members. Con- 
ductors shall comply with 398.17 where passing through 
holes in structural members. Where passing through wood 
cross members in plastered partitions, conductors shall be 
protected by noncombustible, nonabsorbent, insulating 
tubes extending not less than 75 mm (3 in.) beyond the 
wood member. 

394.19 Clearances. 

(A) General. A clearance of not less than 75 mm (3 in.) 
shall be maintained between conductors and a clearance of 
not less than 25 mm (1 in.) between the conductor and the 
surface over which it passes. 

(B) Limited Conductor Space. Where space is too limited 
to provide these minimum clearances, such as at meters, 
panelboards, outlets, and switch points, the individual con- 
ductors shall be enclosed in flexible nonmetallic tubing, 
which shall be continuous in length between the last sup- 
port and the enclosure or terminal point. 

(C) Clearance from Piping, Exposed Conductors, and 
So Forth. Conductors shall comply with 398.19 for clear- 
ances from other exposed conductors, piping, and so forth. 

394.23 In Accessible Attics. Conductors in unfinished at- 
tics and roof spaces shall comply with 394.23(A) or (B). 



FPN: See 310.10 for temperature limitation of conductors. 

(A) Accessible by Stairway or Permanent Ladder. Con- 
ductors shall be installed along the side of or through bored 
holes in floor joists, studs, or rafters. Where run through 
bored holes, conductors in the joists and in studs or rafters 
to a height of not less than 2.1 m (7 ft) above the floor or 
floor joists shall be protected by substantial running boards 
extending not less than 25 mm (1 in.) on each side of the 
conductors. Running boards shall be securely fastened in 
place. Running boards and guard strips shall not be re- 
quired where conductors are installed along the sides of 
joists, studs, or rafters. 

(B) Not Accessible by Stairway or Permanent Ladder. 

Conductors shall be installed along the sides of or through 
bored holes in floor joists, studs, or rafters. 

Exception: In buildings completed before the wiring is in- 
stalled, attic and roof spaces that are not accessible by 
stairway or permanent ladder and have headroom at all 
points less than 900 mm (3 ft), the wiring shall be permitted 
to be installed on the edges of rafters or joists facing the 
attic or roof space. 

394.30 Securing and Supporting. 

(A) Supporting. Conductors shall be rigidly supported on 
noncombustible, nonabsorbent insulating materials and 
shall not contact any other objects. Supports shall be in- 
stalled as follows: 

(1) Within 150 mm (6 in.) of each side of each tap or 
splice, and 

(2) At intervals not exceeding 1.4 m (4V2 ft). 

Where it is impracticable to provide supports, conduc- 
tors shall be permitted to be fished through hollow spaces 
in dry locations, provided each conductor is individually 
enclosed in flexible nonmetallic tubing that is in continuous 
lengths between supports, between boxes, or between a 
support and a box. 

(B) Securing. Where solid knobs are used, conductors 
shall be securely tied thereto by tie wires having insulation 
equivalent to that of the conductor. 



394.42 Devices. 

404.10(B). 



Switches shall comply with 404.4 and 



394.56 Splices and Taps. Splices shall be soldered unless 
approved splicing devices are used. In-line or strain splices 
shall not be used. 

III. Construction Specifications 

394.104 Conductors. Conductors shall be of a type speci- 
fied by Article 310. 



2002 Edition 



NATIONAL ELECTRICAL CODE 



ARTICLE 398 — OPEN WIRING ON INSULATORS 



70-227 



ARTICLE 396 
Messenger Supported Wiring 



I. General 

396.1 Scope. This article covers the use, installation, and 
construction specifications for messenger supported wiring. 

396.2 Definition. 

Messenger Supported Wiring. An exposed wiring support 
system using a messenger wire to support insulated conduc- 
tors by any one of the following: 

(1) A messenger with rings and saddles for conductor sup- 
port 

(2) A messenger with a field-installed lashing material for 
conductor support 

(3) Factory-assembled aerial cable 

(4) Multiplex cables utilizing a bare conductor, factory as- 
sembled and twisted with one or more insulated con- 
ductors, such as duplex, triplex, or quadruplex type of 
construction 



messenger supported wiring, the following shall be per- 
mitted: 

(1) Any of the conductor types shown in Table 310.13 or 
Table 310.62 

(2) MV cable 

Where exposed to weather, conductors shall be listed 
for use in wet locations. Where exposed to direct rays of 
the sun, conductors or cables shall be sunlight resistant. 

(C) Hazardous (Classified) Locations. Messenger sup- 
ported wiring shall be permitted to be used in hazardous 
(classified) locations where the contained cables are permit- 
ted for such use in 501.4, 502.4, 503.3, and 504.20. 

396.12 Uses Not Permitted. Messenger supported wiring 
shall not be used in hoistways or where subject to physical 
damage. 

396.30 Messenger Support. The messenger shall be sup- 
ported at dead ends and at intermediate locations so as to 
eliminate tension on the conductors. The conductors shall 
not be permitted to come into contact with the messenger 
supports or any structural members, walls, or pipes. 



II. Installation 

396.10 Uses Permitted. 

(A) Cable Types. The cable types in Table 396.10(A) shall 
be permitted to be installed in messenger supported wiring 
under the conditions described in the article or section ref- 
erenced for each. 



396.56 Conductor Splices and Taps. Conductor splices 
and taps made and insulated by approved methods shall be 
permitted in messenger supported wiring. 

396.60 Grounding. The messenger shall be grounded as 
required by 250.80 and 250.86 for enclosure grounding. 



Table 396.10(A) Cable Types 



Cable Type 



Section 



Article 



Metal-clad cable 
Mineral-insulated, 

metal-sheathed cable 
Multiconductor 

service-entrance cable 
Multiconductor underground 

feeder and branch-circuit 

cable 
Other factory-assembled, 

multiconductor control, 

signal, or power cables that 

are identified for the use 
Power and control tray cable 
Power-limited tray cable 



330 
332 

338 

340 



336 



725.61(C) and 
725.71(E) 



(B) In Industrial Establishments. In industrial establish- 
ments only, where conditions of maintenance and supervi- 
sion ensure that only qualified persons service the installed 



ARTICLE 3&$^^;^ 
Open Wiring on Insulators 

I. General 

398.1 Scope. This article covers the use, installation, and 
construction specifications of open wiring on insulators. 

398.2 Definition. 

Open Wiring on Insulators. An exposed wiring method 
using cleats, knobs, tubes, and flexible tubing for the pro- 
tection and support of single insulated conductors run in or 
on buildings. 

II. Installation 

398.10 Uses Permitted. Open wiring on insulators shall be 
permitted only for industrial or agricultural establishments 
on systems of 600 volts, nominal, or less, as follows: 



NATIONAL ELECTRICAL CODE 



2002 Edition 



70-228 



ARTICLE 398 — OPEN WIRING ON INSULATORS 



(1) Indoors or outdoors 

(2) In wet or dry locations 

(3) Where subject to corrosive vapors 

(4) For services 

398.12 Uses Not Permitted. Open wiring on insulators 
shall not be installed where concealed by the building 
structure. 

398.15 Exposed Work. 

(A) Dry Locations. In dry locations, where not exposed to 
severe physical damage, conductors shall be permitted to 
be separately enclosed in flexible nonmetallic tubing. The 
tubing shall be in continuous lengths not exceeding 4.5 m 
(15 ft) and secured to the surface by straps at intervals not 
exceeding 1.4 m (4!/2 ft). 

(B) Entering Spaces Subject to Dampness, Wetness, or 
Corrosive Vapors. Conductors entering or leaving loca- 
tions subject to dampness, wetness, or corrosive vapors 
shall have drip loops formed on them and shall then pass 
upward and inward from the outside of the buildings, or 
from the damp, wet, or corrosive location, through non- 
combustible, nonabsorbent insulating tubes. 

FPN: See 230.52 for individual conductors entering build- 
ings or other structures. 

(C) Exposed to Physical Damage. Conductors within 2.1 
m (7 ft) from the floor shall be considered exposed to 
physical damage. Where open conductors cross ceiling 
joists and wall studs and are exposed to physical damage, 
they shall be protected by one of the following methods: 

(1) Guard strips not less than 25 mm (1 in.) nominal in 
thickness and at least as high as the insulating supports, 
placed on each side of and close to the wiring. 

(2) A substantial running board at least 13 mm (V2 in.) 
thick in back of the conductors with side protections. 
Running boards shall extend at least 25 mm (1 in.) 
outside the conductors, but not more than 50 mm 
(2 in.), and the protecting sides shall be at least 50 mm 
(2 in.) high and at least 25 mm (1 in.) nominal in 
thickness. 

(3) Boxing made in accordance with (C)(1) or (C)(2) and 
furnished with a cover kept at least 25 mm (1 in.) away 
from the conductors within. Where protecting vertical 
conductors on side walls, the boxing shall be closed at 
the top and the holes through which the conductors 
pass shall be bushed. 

(4) Rigid metal conduit, intermediate metal conduit, rigid 
nonmetallic conduit, or electrical metallic tubing, in 
which case the rules of Articles 342, 344, 352, or 358 
shall apply; or by metal piping, in which case the con- 
ductors shall be encased in continuous lengths of ap- 
proved flexible tubing. 



398.17 Through or Parallel to Framing Members. Open 
conductors shall be separated from contact with walls, 
floors, wood cross members, or partitions through which 
they pass by tubes or bushings of noncombustible, nonab- 
sorbent insulating material. Where the bushing is shorter 
than the hole, a waterproof sleeve of noninductive material 
shall be inserted in the hole and an insulating bushing 
slipped into the sleeve at each end in such a manner as to 
keep the conductors absolutely out of contact with the 
sleeve. Each conductor shall be carried through a separate 
tube or sleeve. 

FPN: See 310.10 for temperature limitation of conductors. 

398.19 Clearances. Open conductors shall be separated at 
least 50 mm (2 in.) from metal raceways, piping, or other 
conducting material, and from any exposed lighting, power, 
or signaling conductor, or shall be separated therefrom by a 
continuous and firmly fixed nonconductor in addition to the 
insulation of the conductor. Where any insulating tube is 
used, it shall be secured at the ends. Where practicable, 
conductors shall pass over rather than under any piping 
subject to leakage or accumulations of moisture. 

398.23 In Accessible Attics. Conductors in unfinished at- 
tics and roof spaces shall comply with 398.23(A) or (B). 

(A) Accessible by Stairway or Permanent Ladder. 

Conductors shall be installed along the side of or through 
bored holes in floor joists, studs, or rafters. Where run 
through bored holes, conductors in the joists and in studs or 
rafters to a height of not less than 2.1 m (7 ft) above the 
floor or floor joists shall be protected by substantial running 
boards extending not less than 25 mm (1 in.) on each side 
of the conductors. Running boards shall be securely fas- 
tened in place. Running boards and guard strips shall not be 
required for conductors installed along the sides of joists, 
studs, or rafters. 

(B) Not Accessible by Stairway or Permanent Ladder. 

Conductors shall be installed along the sides of or through 
bored holes in floor joists, studs, or rafters. 

Exception: In buildings completed before the wiring is in- 
stalled, attic and roof spaces that are not accessible by 
stairway or permanent ladder and have headroom at all 
points less than 900 mm (3 ft), the wiring shall be permitted 
to be installed on the edges of rafters or joists facing the 
attic or roof space. 

398.30 Securing and Supporting. 

(A) Conductor Sizes Smaller Than 8 AWG. Conductors 
smaller than 8 AWG shall be rigidly supported on noncom- 
bustible, nonabsorbent insulating materials and shall not 



2002 Edition 



NATIONAL ELECTRICAL CODE 



ARTICLE 398 — OPEN WIRING ON INSULATORS 



70-229 



contact any other objects. Supports shall be installed as 
follows: 

(1) Within 150 mm (6 in.) from a tap or splice 

(2) Within 300 mm (12 in.) of a dead-end connection to a 
lampholder or receptacle 

(3) At intervals not exceeding 1.4 m (4V2 ft) and at closer 
intervals sufficient to provide adequate support where 
likely to be disturbed 

(B) Conductor Sizes 8 AWG and Larger. Supports for 
conductors 8 AWG or larger installed across open spaces 
shall be permitted up to 4.5 m (15 ft) apart if noncombus- 
tible, nonabsorbent insulating spacers are used at least ev- 
ery 1.4 m (4'/2 ft) to maintain at least 65 mm (2V2 in.) 
between conductors. 

Where not likely to be disturbed in buildings of mill 
construction, 8 AWG and larger conductors shall be permit- 
ted to be run across open spaces if supported from each 
wood cross member on approved insulators maintaining 
150 mm (6 in.) between conductors. 

(C) Industrial Establishments. In industrial establish- 
ments only, where conditions of maintenance and supervi- 
sion ensure that only qualified persons service the system, 



conductors of sizes 250 kcmil and larger shall be permitted 
to be run across open spaces where supported at intervals 
up to 9.0 m (30 ft) apart. 

(D) Mounting of Conductor Supports. Where nails are 
used to mount knobs, they shall not be smaller than ten- 
penny. Where screws are used to mount knobs, or where 
nails or screws are used to mount cleats, they shall be of a 
length sufficient to penetrate the wood to a depth equal to at 
least one-half the height of the knob and the full thickness 
of the cleat. Cushion washers shall be used with nails. 

(E) Tie Wires. 8 AWG or larger conductors supported on 
solid knobs shall be securely tied thereto by tie wires hav- 
ing an insulation equivalent